Mysql embeddings

[claudevdm]

This PR adds a MySQL vector writer implementation following the same pattern as Postgres vector writer.

• sdks/python/apache_beam/ml/rag/ingestion/mysql.py contains the base MySQL vector writer logic that can be used for any MySQL instance
• sdks/python/apache_beam/ml/rag/ingestion/mysql_common.py contains MySQL dialect utilities for configuring the vector writer, including ColumnSpecs for specifying how Chunk should be mapped to a MySQL schema and ConflictResolution for how inserts that violate uniqueness constraints should be handled
• sdks/python/apache_beam/ml/rag/ingestion/cloudsql.py is a wrapper around the base MySQL vector writer that allows connecting to a CloudSQL instance via the cloudsql socket factory
• sdks/python/apache_beam/ml/rag/ingestion/cloudsql_it_test.py contains tests that cover the base mysql logic. I did not add a base MySQL test to avoid having to spin up mysql database containers and bloating the test infrastructure.

I tried to strike a balance between maintainability of cloudsql specific dialects by not mixing postgres and mysql language utilities while sharing jdbc common utilities and cloudsql common utilities that do not change depending on the dialect.

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[claudevdm]

R: @damccorm

Sorry for the long PR. I am happy to split it into multiple, maybe?

1. Add default schema + tests
2. Add columnspecs (non default schema) + tests
3. Add conflict resolution + tests

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[damccorm]

Thanks - mostly looks good (and very in line with other pieces, which is good)

[claudevdm]

Test failures are related to test containers version change

[Abacn]

This has increased the number of test of https://github.com/apache/beam/actions/workflows/beam_PostCommit_Python_Xlang_Gcp_Dataflow.yml?query=event%3Aschedule from 45 -> 62 causing tests often run exceeds 3h timeout

[claudevdm]

https://github.com/apache/beam/actions/workflows/beam_PostCommit_Python_Xlang_Gcp_Dataflow.yml?query=event%3Aschedule

@Abacn where can I see the list of tests that actually run? I set all of these new tests to be skip on dataflow runner. In the publish test section I see before this change

67 tests found
45 skipped tests found
So that means 22 tests ran?

After this change
84 tests found
62 skipped tests found
Also 22 tests ran?

[claudevdm]

Actually looking back at the test history, it was timing out a lot before this change too.