feat(bqjdbc): implement Per connection logging with Context proxy

[Neenu1995]

b/501081433

1. Foundational MDC & Global File Handler Routing
   Simplifies the BigQueryJdbcMdc ThreadLocal context slots, sets up "Jdbc-global" fallback file routing, and adds isFileLoggingEnabled() to the root logger.

2. Dynamic Context Proxy Wrapper & Connection Wrap
   Implements the BigQueryJdbcContextProxy dynamic proxy interceptor, delegating standard wrappers, and wrapping all new JDBC entries in BigQueryDriver.

3. Statement Modifications & Connection Pool unwrapping
   Adapts Statements and Connection ID builders to utilize the dynamic proxy, and updates connection pool managers to safely extract raw connection properties via standard unwrap calls.

4. 0%-Overhead Raw ResultSet & Metadata Routing
   Completely un-proxies ResultSet to achieve 0% query execution overhead, while implementing targeted ResultSetMetaData proxy wrapping inside getMetaData() to keep metadata queries connection-routed.

5. Decoupled Exceptions & Clean Integration Tests
   Decouples all custom exception constructors to eliminate double-logging, converts all 17 integration test class casts to standard unwrap calls, and migrates all deprecated github_timeline public dataset queries to the active shakespeare dataset.

[gemini-code-assist]

Code Review

This pull request introduces a dynamic proxy mechanism, BigQueryJdbcContextProxy, to automate the management of connection-specific logging contexts (MDC) and unify exception logging across JDBC components. It simplifies the BigQueryJdbcMdc implementation and refactors various classes to remove manual logging overhead. Review feedback suggests extending the proxy to ResultSet to maintain context during data retrieval, handling Object methods within the proxy, correcting the isWrapperFor logic, and improving null-safety in exception message logging.