feat(bigquery-jdbc): add telemetry configuration class

[Neenu1995]

Summary

Introduces the internal TelemetryConfiguration class and builder to manage client-side telemetry settings for the BigQuery JDBC driver.

This is PR 3 of the multi-phase client-side telemetry implementation plan.

Changes Introduced

• TelemetryConfiguration: Immutable configuration class holding upload intervals, batch size thresholds, log source ID, target endpoint, and environment metadata (DriverEnvironment).
• TelemetryConfiguration.Builder: Fluent builder pattern for constructing configuration instances.
• TelemetryConfigurationTest: Unit test suite covering default property initialization, custom property overrides, and equals/hashCode contracts.
• Visibility Scoping: Restricted all classes, builders, getters, and constants to package-private (com.google.cloud.bigquery.jdbc.telemetry.v1) to prevent exposing internal telemetry implementation details outside the driver package.

Default Configuration Parameters

Parameter	Default Value	Description
enabled	true	Telemetry is enabled by default per open-source telemetry guidelines (go/telemetry-oss).
logSource	-1	Placeholder until Clearcut log source ID registration is assigned for BigQuery JDBC.
endpointUrl	https://play.googleapis.com/log	Default Clearcut HTTPS log ingestion endpoint.
uploadIntervalMs	300000 (5 mins)	Periodic background flush interval.
batchSizeThreshold	100	Maximum buffered events before triggering an immediate flush.

[gemini-code-assist]

Code Review

This pull request introduces the TelemetryConfiguration class and its corresponding builder to manage configuration settings for the BigQuery JDBC driver telemetry client. It also includes a comprehensive suite of unit tests in TelemetryConfigurationTest to verify default values, custom configurations, and correct behavior of the equals and hashCode methods. There are no review comments, and the changes look solid.