Move `forc-explore` into its own crate

[mitchmindtree]

As part of an initiative to move plugins unrelated to Sway from the sway repo.

Will need some consideration around fuelup's plugin handling, as well as mdbook doc generation.

[eightfilms]

To close this, the steps here need to be fulfilled:

• [ ] remove forc-explore from CI steps
• [ ] remove the forc-explore directory entirely

[eightfilms]

Since both #2926 and #3163 are merged, this can be closed now.