feat(opencensus-shim) add mapping logic and propagation shim

[aabmass]

Which problem is this PR solving?

Part of #3749 [PR 2 of 5]

Finished state of this feature: #3778

Short description of the changes

Adds some of the basic mapping logic between OpenCensus <-> OpenTelemetry interfaces. This will be used in the next PR (#3756) which adds the Shim tracer and span implementations. As before, I'll update the changelog in the final PR of the series.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Added unit tests for all the functionality

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: aabmass / name: Aaron Abbott (992a052, 8a31f08, 62ae7d0, c3e27ad, 7a272dc, 1110585, 89af775, ad655a9)
• ✅ login: pichlermarc / name: Marc Pichler (3c41bfc)

[codecov]

Codecov Report

Merging #3751 (29abd11) into main (32ae641) will increase coverage by 0.00%.
The diff coverage is 93.22%.

❗ Current head 29abd11 differs from pull request most recent head fbe7d47. Consider uploading reports for the commit fbe7d47 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3751   +/-   ##
=======================================
  Coverage   93.20%   93.20%           
=======================================
  Files         296      298    +2     
  Lines        8998     9057   +59     
  Branches     1853     1864   +11     
=======================================
+ Hits         8387     8442   +55     
- Misses        611      615    +4     

Impacted Files	Coverage Δ
...s/opentelemetry-shim-opencensus/src/propagation.ts	80.00% <80.00%> (ø)
...ges/opentelemetry-shim-opencensus/src/transform.ts	100.00% <100.00%> (ø)

[pichlermarc]

Looks good, thank you for taking the time to work on this. 🙂