feat(bindings/cli): Add --plugin and --cache-root

[titanous]

Description:

• Add --plugin CLI option that takes a plugin/path={"config":"object"} formatted argument and adds the plugin to the jsc.experimental.plugins list (can be used multiple times). If the plugin path is explicitly relative (starts with ./ or ../), then it is converted to an absolute path using the current working directory as the base.
• Add a --cache-root CLI option that sets jsc.experimental.cacheRoot

This is an alternative to #6800 that works better for rules_swc and is more straightforward.

Related issue (if exists): aspect-build/rules_swc#149

[kwonoj]

Techinically, if swcx supports --config, specifying these can be done via --config, is it correct?

[titanous]

There's a field for --config but I don't see any code implementing it.

[kwonoj]

Yes, it is not implemented. My question is should we implement --config instead, by partially supporting plugin first instead of having new top level args.

[titanous]

@kdy1 What do you think about implementing --config vs the approach in this PR?

[kwonoj]

We'll need / have --config anyway, matter of time though. If we add top-level --plugin then once we have --config, what should happen? allow duplicate? or breaking changes to remove duplicated one?

[titanous]

It's easy enough to just append if both flags are used. I can implement --config if that's preferred, I just want to get approval for the path forward before doing more work.

[kdy1]

In this regard, I would like to follow @kwonoj 's opinion.

[titanous]

Superseded by #6835.