Update HangWatcher config

[atuchin-m]

The PR changes the config for HangWatcher that sends a report to backtrace in unexpected hangs:

• disables HangWatcher on Linux (too noisy, hangs in OS-level libs that we can't fix)
• focus on the main process, disable the other process. Hangs for that processes are acceptable and happens in Chromium from time to time. Right now we don't have an instrument to split expected hangs from unwanted.
• enables the feature for 100% of Beta & Nightly

[github-actions]

✅ Test Seed Generated Successfully

To apply the test seed:

1. Desktop: Launch the browser with --variations-pr=1311.
   Android: Set the command line to --variations-pr=1311 in debug menu, restart the browser.
   iOS: Set Variations PR to 1311 in Brave Core Switches debug menu, restart the browser.
2. Wait 5-10 seconds to fetch the seed.
3. Restart the browser to apply the seed.
4. Ensure Active Variations section at brave://version starts with the expected seed version (see below).

Seed Details

Parameter	Value
Version	pull/1311@fefc77ad86bcc3ac35c2b29e7a680782dc378d6d
Uploaded	Wed, 19 Feb 2025 12:37:47 GMT
PR commit	07dd705
Base commit	b323fa4
Merge commit	fefc77a
Serial number	c62e5f86f62a3daa8585235199b2483f