Add "noparent" option to @WithSpan annotation

[lordpixel23]

Is your feature request related to a problem? Please describe.

I have code which is annotated with @WithSpan. Sometimes I want to have a method create a new root span, i.e. to have no parent.

Describe the solution you'd like

Add an attribute to @WithSpan such as noParent=true or type=root or equivalent. This feels similar to how one can set other builder options via the annotation such as being able to set the Span Kind.

Describe alternatives you've considered
I can do this by writing the necessary manual tracing code to create a Span with the setNoParent option on the builder, with all the attendant try/finally scope management, exception capture and remember to call .end() etc. Instead of a simple annotation it ends up taking 10 lines of boilerplate code. OTOH maybe this is a sufficiently rare situation that this is an OK tradeoff.

[mateuszrzeszutek]

Hey @lordpixel23 ,

There is already an open issue for this in the instrumentation project: open-telemetry/opentelemetry-java-instrumentation#1036
Please watch that one; I'll close this as a duplicate.