Use SDK source value in Session Replay MobileSegment.source property

[0xnm]

What does this PR do?

This is to align with what iOS SDK has https://github.com/DataDog/dd-sdk-ios/blob/4dbdf4a10991ba65a02b02bf1fe87e4aa2765b38/DatadogSessionReplay/Sources/Feature/RequestBuilders/SegmentRequestBuilder.swift#L48

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.10%. Comparing base (001c5cb) to head (d041c0a).
Report is 5 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2293      +/-   ##
===========================================
+ Coverage    70.07%   70.10%   +0.03%     
===========================================
  Files          732      732              
  Lines        27227    27209      -18     
  Branches      4579     4575       -4     
===========================================
- Hits         19078    19074       -4     
+ Misses        6873     6861      -12     
+ Partials      1276     1274       -2     

Files with missing lines	Coverage Δ
...sionreplay/internal/net/BatchesToSegmentsMapper.kt	74.49% <100.00%> (ø)
...essionreplay/internal/net/SegmentRequestFactory.kt	100.00% <100.00%> (ø)
...ssionreplay/internal/processor/MobileSegmentExt.kt	100.00% <100.00%> (ø)

... and 34 files with indirect coverage changes