chore: turn `forge coverage` and `forge snapshot` into `forge test` flags (`--coverage`, `--snapshot`)

[zerosnacks]

Component

Forge

Describe the feature you would like

Proposal: merge forge coverage and forge snapshot into forge test, expose them with feature flags (--coverage, --snapshot). This is in line with other reports like --gas-report.

This would simplify forge test compatibility issues described in #9525 and make it easier to flag incompatible flags (current limitation because of TestArgs inheritance)

We should also refactor run_tests method in forge test into helpers

This is a significant breaking change for scripted workflows i.e. https://github.com/atarpara/foundry-snapshot-diff and CI's of users.

[zerosnacks]

Alternatively we could avoid inheriting TestArgs in coverage and implement a subset - like ScriptArgs does and implement a subset of run_tests