feat(cheatcodes): vm.skip(bool) for skipping tests

[Evalir]

Motivation

Closes #1123

Solution

Adds a vm.skip(bool) cheatcode that marks tests as skipped. It also moves the test runner to use a TestStatus enum to mark success, failure, or a skipped test, which is the bulk of the work here really.

• On normal tests, this will just check if it failed due to a skip.
• On fuzz tests, it will fuzz with only one run and check the revert reason.
• On invariant tests, it will run once and check if it failed due to a skip, like a normal test.

One thing I noticed is that the handling and return types between normal/invariant/fuzz tests are pretty different. When we revisit the test runner we should try and streamline the handling of all of these so we can properly detect EVM errors in an easier way.

TODO:

• Implement vm.skip(bool)
• Works on normal tests
• Works on fuzz tests
• Works on invariant tests
• Make magic bytes detection and marking as skipped cleaner by not repeating code

Sample output:

[mattsse]

lgtm

[Evalir]

@mds1 I think we'll merge this initial version that only works at the test level to keep test runner changes minimal—adding a reason string or making it work correctly at the set up level could involve moving a bit more code and I'd like to add this incrementally in another PR

[shazow]

Thank you for working on this. :)