Update callers of GetBufLockFileForPrefix to pass a resolve function

[oliversun9]

This is a followup to 39f0510, passing the BufLockFileWithDigestResolver option whenever possible.

• Add helper to bufmoduleapi:

func CommitIDToDigest(
	ctx context.Context,
	clientProvider bufapi.ClientProvider,
	remote string,
	commitID string,
) (bufcas.Digest, error)

• Pass a client provider to callers of GetBufLockFileForPrefix. These callers can then pass

func(ctx context.Context, remote string, commitID string) (bufcas.Digest, error) {
	return bufmoduleapi.CommitIDToDigest(ctx, p.clientProvider, remote, commitID)
},

as the resolve function.

In the future, to make fewer network calls, we could have a CommitResolver and create it with

NewCommitResolver(..., clientProvider, hints)

where hints are potential commit IDs to resolve.

[oliversun9]

It feels awkward to just pass a nil, should I create some NewNopClientProvider helper?

[bufdev]

yea

[bufdev]

I would actually not pass it to the moduleDataStore, and instead add a comment that we expect all lock files in the moduleDataStore to have digests. We control this.

[bufdev]

Mostly looks good, this was less ugly than I thought, see two comments (add a no-op ClientProvider, do not pass to ModuleDataStore)

[bufdev]

I would add a comment in ModuleDataStore about why we are not passing the option as well.

[bufdev]

Nit: In other places, we just do var NopClientProvider ClientProvider = nopClientProvider{} as a global variable, and then you don't have any constructors, and you implement the functions directly on the struct, not the struct pointer, ie func (nopClientProvider) BranchServiceClient...