[FR] Improve error messaging for Table type mismatches

[paulramsey]

• Is this a bug or feature request? Feature Request (Enhancement)
• Current Behavior: When a field type does not match the Spanner table definition (e.g., String vs Boolean in Table), the client throws a generic INVALID_ARGUMENT: invalid mutation key error. This makes debugging difficult as it does not specify which column caused the failure.
• Expected Behavior: The exception should ideally identify the specific column name and the type mismatch (e.g., "Expected BOOL for column 'isValid', but received STRING").
• Example (unhelpful) Error:

Caused by: com.google.cloud.spanner.SpannerException: INVALID_ARGUMENT: io.grpc.StatusRuntimeException: INVALID_ARGUMENT: Failed to initialize transaction due to invalid mutation key. - RequestId: 1.e93046ae8a546107.1.1.112.1
      at com.google.cloud.spanner.SpannerExceptionFactory.newSpannerExceptionPreformatted(SpannerExceptionFactory.java:359)
      at com.google.cloud.spanner.SpannerExceptionFactory.fromApiException(SpannerExceptionFactory.java:379)
      at com.google.cloud.spanner.SpannerExceptionFactory.newSpannerException(SpannerExceptionFactory.java:192)
      at com.google.cloud.spanner.SpannerExceptionFactory.newSpannerException(SpannerExceptionFactory.java:115)
      at com.google.cloud.spanner.SessionImpl.lambda$beginTransactionAsync$3(SessionImpl.java:507)
      ... 51 more