feat: Add CLP_GET_* UDFs with rewrites for schemaless querying.

[wraymo]

Description

This PR introduces new user-defined functions (UDFs) for the CLP connector to improve querying of semi-structured logs:

CLP_GET_* functions for retrieving values from JSON paths, targeting specific CLP column types (ClpString, Integer, Float, etc.). These UDFs enable direct access to dynamic fields and return corresponding Presto native types.
They are integrated with the query rewriting layer. During query optimization, calls to these functions are rewritten into normal column references or KQL query column symbols, ensuring efficient execution with no additional parsing overhead.

The PR doesn't update the documentation and will leave it for a future PR.

Checklist

• The PR satisfies the contribution guidelines.
• This is a breaking change and that has been indicated in the PR title, OR this isn't a
  breaking change.
• Necessary docs have been updated, OR no docs need to be updated.

Validation performed

All unit tests passed. End-to-end testing worked.

Summary by CodeRabbit

• New Features

  • Added placeholder scalar CLP functions for typed JSON-path extraction and registered them with the CLP plugin.
  • Added a plan rewriter to translate CLP UDFs into query variables to enable optimization and pushdown.

• Refactor

  • Reorganized optimizer and converter components; centralized filter pushdown and extended it to cover metadata filters.
  • Simplified converter APIs by encapsulating variable-to-column mappings.

• Tests

  • Added integration tests for UDF rewriting and compute-pushdown; improved test setup.

• Chores

  • Expanded test-scoped dependencies and updated native-execution submodule pointer.