Add submodule pin check to CI

[Tristan-Wilson]

This checks that submodules are ancestors of origin/HEAD or a configurable expected branch so that non-merged branches aren't accidentally checked in.

Fixes NIT-2604

Initially this will likely FAIL because we have some submodules that are not under origin/HEAD.

Testing done

This screenshot shows an example of what you see when it fails:

[Tristan-Wilson]

Updated the arbitrator/langs/bf pin as it was fairly clear what to do.

For the following I need experts on these submodules to take a look
arbitrator/langs/c pin is 6 months ahead of origin/HEAD
arbitrator/langs/rust is on a branch diverging from origin/HEAD
arbitrator/tools/wasmer is ahead of origin/HEAD
contracts is several months ahead of origin/HEAD
fastcache is several months ahead of origin/HEAD

@PlasmaPower @tsahee @magicxyyz @rachel-bousfield

[eljobe]

LGTM

[PlasmaPower]

• I merged fastcache (it was just one small change, Merge go-wasi into master fastcache#2 )
• contracts should target the develop branch as upstream. Is it behind that?
• For wasmer, I think @tsahee should probably review Adopt v4.2.8 wasmer#7 . It's been approved by Josh already but it's already in the nitro pin and it'd probably be good to make sure this is solid.
• For arbitrator/langs/*, these are mainly about testing
  • For the C SDK, it looks like OffchainLabs/stylus-sdk-c@stylus...vm-storage-cache needs merged, cc @tsahee @rachel-bousfield . It looks to me like the latest stylus branch of the C SDK is incompatible with current nitro master because the host IOs look different.
  • For the Rust SDK, it looks like this pins VM Storage Cache stylus-sdk-rs#115 but I'm not sure if this PR is still relevant, cc @tsahee @rachel-bousfield as it looks like the latest stylus branch already has the corresponding host IO changes. @Tristan-Wilson I'd try pinning the stylus branch instead in the nitro repo and see if tests and CI still pass.
  • Both of these changes seem to be about the "VM storage cache", which I don't know much about.

[Tristan-Wilson]

I merged fastcache

I made a PR to update nitro pin and will merge it back into this PR once it's merged
#2457

• contracts should target the develop branch as upstream. Is it behind that?

We should change the default GH branch to develop instead of main and the check will pass.