fix(cheatcodes): skip gas snapshots if not in isolation mode

[zerosnacks]

Motivation

Opened for visibility

Ref: #9477 (comment)

Gas snapshots are not accurate outside of isolation mode and we've seen users only run gas snapshots with isolation mode enabled for this reason.

When running a test without --isolate enabled and gas snapshots cheatcodes are active a warning is raised similar to the deprecated cheatcodes (on per cheatcode used per test suite, collected at the end)

This PR also fixes the issue where previously a single test from a test suite or custom group would clear out all the other keys. This has now been changed so that we merge with the previous results, replacing existing keys if they were effected. Note: this comes at the cost of now staining old values. This was deemed preferable based on feedback we received.

Solution

This PR adds a requires keyword for the Cheatcodes spec which lets the developer indicate on prerequisites are required to run a cheatcode. In this can it is isolation mode for the gas snapshots.

To do:

• Decide whether to require snapshotValue to also be ran in isolation mode given it is for arbitrary values. Because of its existence users still run into the "running one test overwrites the all related snapshot results"

Not added, this should run regardless

• Fix tests
• Test if the skipping works correctly when in-line configs are used
• Running a single related test should merge its results, replacing only its own result and leaving the others intact (note that this does cause staining!)