RUM-15877: Add fed2 endpoint to DatadogSite

[aleksandr-gringauz]

Cherry-picking #3383 to the release/3.9.0 branch.

What does this PR do?

A brief description of the change being made with this pull request.

Motivation

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Additional Notes

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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 71.84%. Comparing base (f47ab32) to head (0864a59).

Additional details and impacted files

@@                Coverage Diff                @@
##           release/3.9.0    #3391      +/-   ##
=================================================
- Coverage          71.96%   71.84%   -0.12%     
=================================================
  Files                948      948              
  Lines              34952    34951       -1     
  Branches            5804     5804              
=================================================
- Hits               25152    25109      -43     
- Misses              8226     8253      +27     
- Partials            1574     1589      +15     

Files with missing lines	Coverage Δ
...src/main/kotlin/com/datadog/android/DatadogSite.kt	100.00% <100.00%> (ø)
...og/android/flags/internal/DatadogSiteExtensions.kt	100.00% <100.00%> (ø)

... and 33 files with indirect coverage changes

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