Bytecode version upgrade for invokedynamic dispatch

[SylvainJuge]

When using the invokedynamic dispatching strategy described in #8999, it requires the instrumented classes to at least have been compiled with Java 7 (51) in order to use the invokedynamic instruction.

This transformer allows to upgrade the instrumented classes bytecode to Java 7 (51).

Implementation checklist

• testing with bytecode from java 1 to java 8
• using generated bytecode as newer JDKs do not allow this.

Usage

This PR only adds and tests one AgentBuilder.Transformer, it is not yet applied on every instrumentation, that will be done in a later PR. Doing that will require to add this transformer in the io.opentelemetry.javaagent.tooling.instrumentation.InstrumentationModuleInstaller#install method.

[tylerbenson]

I think it would help to indicate in the description how you intend to hook this in, otherwise seems ok to me.

[SylvainJuge]

I think it would help to indicate in the description how you intend to hook this in, otherwise seems ok to me.

@tylerbenson I've updated the PR description with an Usage section, let me know if you need more details or if that's enough for now.