Improve metrics collector

[StaehliJ]

Pull request

Description

The goal of this PR is to measure metric for each session for consistency.

Changes made

• Self-Explanatory

Checklist

• Your branch has been rebased onto the main branch.
• APIs have been properly documented (if relevant).
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).
• All pull request status checks pass.

[github-actions]

Code Coverage

Overall Project	53.5% -0.86%	🟢
Files changed	76.12%	🟢

Module	Coverage
:pillarbox-player	59.26% -1.61%	🟢

Files

Module	File	Coverage
:pillarbox-player	PlaybackMetrics.kt	97.39% -2.61%	🟢
	SessionMetrics.kt	88.58% -11.42%	🟢
	QoSCoordinator.kt	85.68%	🟢
	MetricsCollector.kt	68.49% -30.31%	🟢

[MGaetan89]

Some minor comments/questions, but looks good otherwise.
From a quick testing, it seems to be working fine 👍🏻