feat: Metrics tracer addAttribute map overload

[surbhigarg92]

This PR adds an overload for adding multiple attributes at once.

Earlier the client had to call the addAttributes method in a loop to add each attributes. Below overload takes a map and add all the attributes at once

public void addAttributes(Map<String, String> attributes) {
    this.attributes.putAll(attributes);
  };

[sonarcloud]

Quality Gate passed for 'gapic-generator-java-root'

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarcloud]

Quality Gate failed for 'java_showcase_integration_tests'

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud

[blakeli0]

/gcbrun

[lqiu96]

@surbhigarg92

I believe we're seeing some downstream errors in Java-Spanner related to this PR:

Error:  Failures: 
Error:    CompositeTracerTest.testMethodsOverrideMetricsTracer:238 Method not found in compositeTracerMethods: public void com.google.api.gax.tracing.MetricsTracer.addAttributes(java.util.Map)

From a quick glance, it seems like test expects the CompositeTracer to have an override for addAttributes(java.util.Map). Is this something that Spanner is planning on adding or is there a way to resolve this error in Spanner's tests (or maybe a different resolution)?

CC: @JoeWang1127

[surbhigarg92]

@surbhigarg92

I believe we're seeing some downstream errors in Java-Spanner related to this PR:

Error:  Failures: 
Error:    CompositeTracerTest.testMethodsOverrideMetricsTracer:238 Method not found in compositeTracerMethods: public void com.google.api.gax.tracing.MetricsTracer.addAttributes(java.util.Map)

From a quick glance, it seems like test expects the CompositeTracer to have an override for addAttributes(java.util.Map). Is this something that Spanner is planning on adding or is there a way to resolve this error in Spanner's tests (or maybe a different resolution)?

CC: @JoeWang1127

@lqiu96 Will be fixing this in Spanner