Making resource bounds the default instead of timeouts

[marcoeilers]

• Making resource bounds the default instead of the current timeouts for checks. This removes the main source of non-determinism when using Silicon.
• Replacing the old flag --proverEnableResourceBounds with a new flag --proverEnableTimeBounds, which can be used to get the old behavior.
• Also doing some cleanup and removing old options whose names are Z3-specific (--z3X), which have been deprecated forever, and for which there are generic alternatives (--proverX).
• For time to resource conversions, we add different options for Z3 and CVC5, because their resources work differently. I'm reasonably certain that the Z3 conversion rate is decent, I'm much less certain about the CVC5 one.

Tested with:

• Nagini tests in CI and on my laptop
• SCION router on my laptop
• Viper tests in CI and on my laptop
• Gobra tests on my laptop
• Prusti tests on my laptop
  For all those, the change did not add spurious errors and only slightly changed overall verification time.