Allow to start_as_current_span with end_on_exit=False

[anton-ryzhov]

Description

start_as_current_span is just a helper that combines start_span and use_span methods. But it doesn't allow to change end_on_exit attribute. When it's required user have to call two underlying methods explicitly. Wrapper should expose all attributes to cover all cases.

Example use case:

def demo():
    with tracer.start_as_current_span('task', end_on_exit=False) as span:
        # Do some synchronous task preparation 
        # that must be part of the span
        task_data = ...

        # Contunue asynchronously
        executor.submit(
            tracer.use_span(span, use_span=True)(task_handler),
            task_data,
        )

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Unit tests updated respectively

Does This PR Require a Contrib Repo Change?

Answer the following question based on these examples of changes that would require a Contrib Repo Change:

• The OTel specification has changed which prompted this PR to update the method interfaces of opentelemetry-api/ or opentelemetry-sdk/

• The method interfaces of opentelemetry-instrumentation/ have changed

• The method interfaces of test/util have changed

• Scripts in scripts/ that were copied over to the Contrib repo have changed

• Configuration files that were copied over to the Contrib repo have changed (when consistency between repositories is applicable) such as in

  • pyproject.toml
  • isort.cfg
  • .flake8

• When a new .github/CODEOWNER is added

• Major changes to project information, such as in:

  • README.md
  • CONTRIBUTING.md

• Yes. - Link to PR:

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated