Make sure trace flags are parsed properly when extracting traceparent and expand tests

[deejgregor]

Description

This PR does two things:

1. Make sure trace flags are parsed properly when extracting traceparent
2. Expands tests for traceparent parsing (including the above issue) and trace flags handling.

Fixes # (issue) (no current issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• The test which exercises the traceparent trace flags parsing issue is test_extract_non_decimal_trace_flags in opentelemetry-api/tests/propagators/test_propagators.py and passes with the change to opentelemetry-api/src/opentelemetry/trace/propagation/tracecontext.py.
• Added a number of other unit tests to exercise related functionality.

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 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