Tidy up `implementations`, `semver.yaml` and associated code.

[mds1]

Per superchain a set of canonical implementation deployments, per semver version, is tracked.
As default, an empty collection of deployments can be set:

I think this should be tweaked to clarify that it's the "governance approved standard implementations starting from op-contracts/v1.3.0 and later" (i.e. MCP and later and only applies to standard + premier chains). In which case I agree with the /superchain/implementations @ethereum-optimism/security-reviewers assignment

Originally posted by @mds1 in #163 (comment)

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Update: we have no implemented an entirely new way of checking contract versions.

This ticket now covers removing cruft from the old way of doing it, as well as other files which are only referenced in the deprecated op-upgrade package (which also needs to be removed).

[geoknee]

This could be considered a duplicate of #289

[geoknee]

In favour of #331