Give instrumentations of stdlib packages a separate symbol so know when to use instrumentation pkg

This came up in a comment on my recent PR: https://github.com/open-telemetry/opentelemetry-python-contrib/pull/739#discussion_r735728575

Is your feature request related to a problem?
The aws_lambda instrumentation does not need to have any dependency packages installed for it to instrument AWS Lambda, but obviously is only applicable in the AWS Lambda environment.

This means with no dependencies, it is on the same design as instrumentations of stdlib packages. However, stdlib packages should always be instrumented because they're packages are available in the standard distribution of python.

Describe the solution you'd like

As suggested by @owais, we could add a opentelemetry.instrumentation.symbols.STDLIB symbol to distinguish them.

Describe alternatives you've considered
Which alternative solutions or features have you considered?

Additional context
In a quick search of the specifications I didn't find mention of this. Should I be discussing this there? It seems like something other SIGs would run into.

Start with the proposed opentelemetry.instrumentation.symbols.STDLIB entry and review how instrumentation packages currently identify their dependencies or environment requirements. Confirm which stdlib instrumentations need the distinction, then update the relevant categorization and tests so the new symbol clearly separates them from environment-specific packages.