junos_linkagg implementation and junos modules refactor (#26587)

* junos_linkagg implementation and junos modules refactor

*  junos_linkagg implementation
*  junos_linkagg integration test
*  net_linkagg integration test for junos
*  decouple `load_config` and `commit` operations,
   to allow single commit (in case on confirm commit) and
   to perform batch commit (multiple `load_config` followed by single
   `commit`)
*  Other related refactor

* Fix CI issues

* Fix unit test failure

test/integration/targets/junos_linkagg/tasks/main.yaml

@@ -0,0 +1,2 @@
+---
+- { include: netconf.yaml, tags: ['netconf'] }

test/integration/targets/junos_linkagg/tasks/netconf.yaml

@@ -0,0 +1,16 @@
+---
+- name: collect all netconf test cases
+  find:
+    paths: "{{ role_path }}/tests/netconf"
+    patterns: "{{ testcase }}.yaml"
+  register: test_cases
+  delegate_to: localhost
+
+- name: set test_items
+  set_fact: test_items="{{ test_cases.files | map(attribute='path') | list }}"
+
+- name: run test case
+  include: "{{ test_case_to_run }}"
+  with_items: "{{ test_items }}"
+  loop_control:
+    loop_var: test_case_to_run