RUM-4418: Don't mark internal extension functions for 3rd party types as 3rd party

[0xnm]

What does this PR do?

Fix for the long-standing issue: UnsafeThirdPartyFunctionCall was marking internal extension functions for third-party types as third-party functions, which is wrong. This PR fixes that by checking the declaration package for the function in addition to its container.

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

Merging #1996 (9263a25) into develop (18967d7) will decrease coverage by 0.01%. Report is 12 commits behind head on develop. The diff coverage is n/a.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1996 +/- ## =========================================== - Coverage 83.66% 83.65% -0.01% =========================================== Files 488 488 Lines 17770 17730 -40 Branches 2663 2661 -2 =========================================== - Hits 14867 14832 -35 + Misses 2178 2177 -1 + Partials 725 721 -4 ``` [see 29 files with indirect coverage changes](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/1996/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog)