[CI] Tune test timeouts

[kciesielski]

Here's another attempt to make this better.
After recent change which moves test compilation to the compileScoped step (#3336), I noticed that the Test step takes much less time (yay!). It's now a matter of minutes, usually far less than 10m if successful.
Because of this, I propose:

1. Reducing timeout: if tests freeze, let's retry after 15 minutes instead of 45 minutes
2. Increasing number of retries: let's bump this a bit, from 3 to 4

[adamw]

Looks good, let's try :)