Add log payload models

[fractalwrench]

Goal

Adds model classes for the new log payloads. This is mostly generated via OpenAPI but tweaked manually for style reasons.

Testing

Added unit test to confirm new model can be constructed from old one.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 79.44%. Comparing base (5c198c4) to head (68fbe61).

Additional details and impacted files

@@                 Coverage Diff                  @@
##           add-span-payload     #522      +/-   ##
====================================================
+ Coverage             79.42%   79.44%   +0.01%     
====================================================
  Files                   399      403       +4     
  Lines                 10835    10855      +20     
  Branches               1600     1600              
====================================================
+ Hits                   8606     8624      +18     
- Misses                 1583     1586       +3     
+ Partials                646      645       -1     

Files	Coverage Δ
...embrace/android/embracesdk/internal/payload/Log.kt	100.00% <100.00%> (ø)
...ace/android/embracesdk/internal/payload/LogBody.kt	100.00% <100.00%> (ø)
...e/android/embracesdk/internal/payload/LogMapper.kt	100.00% <100.00%> (ø)
.../android/embracesdk/internal/payload/LogPayload.kt	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes