Update Gradle to 8.7, AGP to 8.4.0

[0xnm]

What does this PR do?

This PR updates Gradle version to 8.7 and AGP to 8.4.0 in 2 different commits: one updates it for the build env, another one updates it for the functional tests run.

This PR also removes Detekt from the build script - it is run externally in the static-analysis nested pipeline and it was using old version 1.17.0, which doesn't work with the change made.

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 81.42%. Comparing base (5368d30) to head (284cc34).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #253      +/-   ##
=============================================
+ Coverage      81.38%   81.42%   +0.05%     
- Complexity       202      204       +2     
=============================================
  Files             26       26              
  Lines            800      802       +2     
  Branches         103      104       +1     
=============================================
+ Hits             651      653       +2     
  Misses           112      112              
  Partials          37       37              

see 2 files with indirect coverage changes