[java-bigtable] Replace the usage of BaseApiTracer and BaseApiTracerFactory with ApiTracer and ApiTracerFactory

As part of the OpenTelemetry metrics project, we made all methods in `ApiTracer` default in this [PR](https://github.com/googleapis/sdk-platform-java/pull/2403/files#diff-7c0438b5f6b77d8cf3f1bf3eb9c4550c8a47852bbf16c42a367797c48f3f584f). Since `BaseApiTracer` was originally introduced for Java 7 compatibility and we dropped Java 7 support now, we can replace the usage of `BaseApiTracer` and `BaseApiTracerFactory` with `ApiTracer` and `ApiTracerFactory`.
For example, make `BigtableTracer` implements `ApiTracer` instead of [extending from BaseApiTracer](https://github.com/googleapis/java-bigtable/blob/3f37d8da8b51a3fea56d1c462b9500ee2c244973/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/metrics/BigtableTracer.java#L29).

Start with google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/metrics/BigtableTracer.java and search the repository for usages of BaseApiTracer and BaseApiTracerFactory. The work is done when those usages are replaced with ApiTracer and ApiTracerFactory throughout the Java Bigtable code.

Written by the indexing model from the issue text.