legacy subcommand & CLI structure refactor

[Bushuo]

This PR refactors the CLI structure of rewatch to enhance clarity and improve the usability of subcommands and their associated arguments.

Key Changes:

Introduction of New Subcommands:

• legacy: Acts as a passthrough to the legacy CLI rescript. In the future, this will be named rescript-legacy.
• dump: Serves as an alias for legacy dump.
• format: Serves as an alias for legacy format.

Breaking Change:
The --compiler-args argument has been replaced with a new subcommand compiler-args. I assume this change will have minimal impact. I guess this is mainly used as a debug command.

Benefits:

The refactored structure ensures a more intuitive CLI experience by clearly delineating which arguments apply to specific subcommands.
The introduction of aliases (dump and format) simplifies common operations and aims to make the transition to rewatch as the default build system easier.
The new compiler-args subcommand makes the CLI behavior more consistent and predictable.

[Bushuo]

@jfrolich It seems to be running a bit slower now, but I don't understand why it would be.
The performance is only measured starting in build but I did not touch anything in there and deeper.

[jfrolich]

Only in this PR? Or is the performance hit potentially introduced earlier?

[Bushuo]

Only in this PR? Or is the performance hit potentially introduced earlier?

I noticed it because the snapshots are different. I think it is only this PR.

[Bushuo]

@jfrolich I had a misunderstanding and --no-timing did not work as intended.
The tests are passing but there is a further change.
Calls like rewatch --no-timing build are discouraged now because the build part will be treated as folder arg.

The confusion stemmed from --no-timing printing the timings as 0.0s.
Maybe we should make it omit the timing info.