Apply configured service name mapping to DBM-injected dddbs

[vandonr]

What Does This Do

The injected dddbs tag should respect service mapping.

For single statements, we create the span and inject the comment in the same instrumentation, so everything is well (code)
However, for prepared statements, it's more complicated, because it happens in 2 steps:

• step 1: the call to prepare is instrumented, this is where we inject the comment, it's done in DBMCompatibleConnectionInstrumentation
• step 2: the call to execute is instrumented, this is when the command is actually run, so this is where we create the span (this is done in AbstractPreparedStatementInstrumentation)
  Thus, we don't have the span yet when we do the injection for prepared statements.

Service mapping logic was only applied when a service name is set in a span:

dd-trace-java/dd-trace-core/src/main/java/datadog/trace/core/DDSpanContext.java

Lines 398 to 401 in ad66ae8

	public void setServiceName(final String serviceName) {
	this.serviceName = trace.mapServiceName(serviceName);
	this.topLevel = isTopLevel(parentServiceName, this.serviceName);
	}

so if we get a service name not from a span, the mapping wouldn't be applied to it.

To fix this, I'm repeating the logic that is found here:

dd-trace-java/dd-trace-core/src/main/java/datadog/trace/core/PendingTrace.java

Line 173 in 0779b79

return traceConfig.getServiceMapping().getOrDefault(serviceName, serviceName);

@mcculls helped with the code to retrieve the current trace's config snapshot.

Jira ticket: APMS-12191

fixes #7034

[amarziali]

Would it be possible to add tests?

[vandonr]

Would it be possible to add tests?

yes I'll look into it. For now, it seems there might be some tests failing, that I cannot reproduce locally :(
I was hoping to draw inspiration from there.

[amarziali]

LGTM. I left some suggestions