Let fields be sent raw in table schema definition

As per https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#TableFieldSchema
the `fields` attribute can recursively define more fields if the `type`
attribute is RECORD. There is no way to define recursive argument spec
in ansible modules, but if sent as `raw`:

> The raw type, performs no type validation or type casting, and maintains the type of the passed value.

(from https://docs.ansible.com/ansible/latest/dev_guide/developing_program_flow_modules.html#argument-spec)

Which works for what we're trying to accomplish here.

Also added integration test for this change

plugins/modules/gcp_bigquery_table.py

@@ -181,7 +181,7 @@ options:
           fields:
             description:
             - Describes the nested schema fields if the type property is set to RECORD.
-            elements: str
+            elements: raw
             required: false
             type: list
           mode:
@@ -296,7 +296,7 @@ options:
                 description:
                 - Describes the nested schema fields if the type property is set to
                   RECORD .
-                elements: str
+                elements: raw
                 required: false
                 type: list
               mode:
@@ -1045,7 +1045,7 @@ def main():
                         elements='dict',
                         options=dict(
                             description=dict(type='str'),
-                            fields=dict(type='list', elements='str'),
+                            fields=dict(type='list', elements='raw'),
                             mode=dict(type='str'),
                             name=dict(type='str'),
                             type=dict(type='str'),
@@ -1072,7 +1072,7 @@ def main():
                                 elements='dict',
                                 options=dict(
                                     description=dict(type='str'),
-                                    fields=dict(type='list', elements='str'),
+                                    fields=dict(type='list', elements='raw'),
                                     mode=dict(type='str'),
                                     name=dict(type='str'),
                                     type=dict(type='str'),

tests/integration/targets/gcp_bigquery_table/tasks/main.yml

@@ -1,3 +1,8 @@
 ---
 - name: Generated tests
   ansible.builtin.include_tasks: autogen.yml
+
+- name: Run nested test cases
+  ansible.builtin.include_tasks: nested.yml
+  vars:
+    dataset_name: "{{ resource_name | replace('-', '_') }}_nested"

tests/integration/targets/gcp_bigquery_table/tasks/nested.yml

@@ -0,0 +1,92 @@
+---
+- name: Run testcases
+  block:
+    - name: create dataset
+      google.cloud.gcp_bigquery_dataset:
+        name: "{{ dataset_name }}"
+        dataset_reference:
+          dataset_id: "{{ dataset_name }}"
+        project: "{{ gcp_project }}"
+        auth_kind: "{{ gcp_cred_kind }}"
+        service_account_file: "{{ gcp_cred_file }}"
+        state: present
+      register: _dataset
+
+    - name: Create table with defined fields
+      google.cloud.gcp_bigquery_table:
+        name: "{{ resource_name }}-fields"
+        dataset: "{{ dataset_name }}"
+        state: present
+        project: "{{ gcp_project }}"
+        auth_kind: "{{ gcp_cred_kind }}"
+        service_account_file: "{{ gcp_cred_file }}"
+        table_reference:
+          dataset_id: "{{ dataset_name }}"
+          project_id: "{{ gcp_project }}"
+          table_id: "{{ resource_name }}-fields"
+        schema:
+          fields:
+            - name: id
+              description: An Integer field
+              type: INTEGER
+            - name: name
+              description: A String field
+              type: STRING
+
+    - name: Create table with nested fields
+      google.cloud.gcp_bigquery_table:
+        name: "{{ resource_name }}-nested"
+        dataset: "{{ dataset_name }}"
+        state: present
+        project: "{{ gcp_project }}"
+        auth_kind: "{{ gcp_cred_kind }}"
+        service_account_file: "{{ gcp_cred_file }}"
+        table_reference:
+          dataset_id: "{{ dataset_name }}"
+          project_id: "{{ gcp_project }}"
+          table_id: "{{ resource_name }}-nested"
+        schema:
+          fields:
+            - name: id
+              description: An Integer field
+              type: INTEGER
+            - name: def
+              description: A Record field
+              type: RECORD
+              fields:
+                - name: id
+                  description: A nested Integer field
+                  type: INTEGER
+                - name: subdef
+                  description: A nested Record field
+                  type: RECORD
+                  fields:
+                    - name: id
+                      description: A nested-nested Integer field
+                      type: INTEGER
+                    - name: desc
+                      description: A nested-nested String field
+                      type: STRING
+
+  always:
+    - name: Remove tables
+      google.cloud.gcp_bigquery_table:
+        name: "{{ resource_name }}-{{ item }}"
+        dataset: "{{ dataset_name }}"
+        project: "{{ gcp_project }}"
+        auth_kind: "{{ gcp_cred_kind }}"
+        service_account_file: "{{ gcp_cred_file }}"
+        state: absent
+      loop:
+        - fields
+        - nested
+
+    - name: Remove dataset
+      google.cloud.gcp_bigquery_dataset:
+        name: "{{ dataset_name }}"
+        dataset_reference:
+          dataset_id: "{{ dataset_name }}"
+        project: "{{ gcp_project }}"
+        auth_kind: "{{ gcp_cred_kind }}"
+        service_account_file: "{{ gcp_cred_file }}"
+        state: absent