Embed pymysql within the collection and use default test container

This change eliminates the need to install the connector on each
controlled node, as `pymysql` version 1.1.1 is now included. As a
result, we can safely assume its availability, thus simplifying the
testing process.

Also, I managed to remove the need for pre-built test containers. We
now use the default test containers from ansible-test.

plugins/module_utils/pymysql/constants/CLIENT.py

@@ -0,0 +1,38 @@
+# https://dev.mysql.com/doc/internals/en/capability-flags.html#packet-Protocol::CapabilityFlags
+LONG_PASSWORD = 1
+FOUND_ROWS = 1 << 1
+LONG_FLAG = 1 << 2
+CONNECT_WITH_DB = 1 << 3
+NO_SCHEMA = 1 << 4
+COMPRESS = 1 << 5
+ODBC = 1 << 6
+LOCAL_FILES = 1 << 7
+IGNORE_SPACE = 1 << 8
+PROTOCOL_41 = 1 << 9
+INTERACTIVE = 1 << 10
+SSL = 1 << 11
+IGNORE_SIGPIPE = 1 << 12
+TRANSACTIONS = 1 << 13
+SECURE_CONNECTION = 1 << 15
+MULTI_STATEMENTS = 1 << 16
+MULTI_RESULTS = 1 << 17
+PS_MULTI_RESULTS = 1 << 18
+PLUGIN_AUTH = 1 << 19
+CONNECT_ATTRS = 1 << 20
+PLUGIN_AUTH_LENENC_CLIENT_DATA = 1 << 21
+CAPABILITIES = (
+    LONG_PASSWORD
+    | LONG_FLAG
+    | PROTOCOL_41
+    | TRANSACTIONS
+    | SECURE_CONNECTION
+    | MULTI_RESULTS
+    | PLUGIN_AUTH
+    | PLUGIN_AUTH_LENENC_CLIENT_DATA
+    | CONNECT_ATTRS
+)
+
+# Not done yet
+HANDLE_EXPIRED_PASSWORDS = 1 << 22
+SESSION_TRACK = 1 << 23
+DEPRECATE_EOF = 1 << 24