[on hold till next version] Port getOwnersByPage to an extension

[HardlyDifficult]

Description

Creates a LockInspector extension contract. I started with just getOwnersByPage but there may be other functions to port over - or just to add for convenience.

A small simplification to the lock contract and saves us a bit of space.

The tests are basically what we had previously, but I also removed the revert for this read-only call.

Issues

Fixes #
Refs #6010

Checklist:

• 1 PR, 1 purpose: my Pull Request applies to a single purpose
• I have commented my code, particularly in hard-to-understand areas
• I have updated the docs to reflect my changes if applicable
• I have added tests (and stories for frontend components) that prove my fix is effective or that my feature works
• I have performed a self-review of my own code
• If my code involves visual changes, I am adding applicable screenshots to this thread

[HardlyDifficult]

Reduces PublicLock deployment by 90.5k gas. I'm unsure how much that is in terms of our byte limit.

[nfurfaro]

Looks good. We could possibly add the utils functions in UnlockUtils.sol (only used for metadata) as well.

[HardlyDifficult]

UnlockUtils.sol

That's an internal library atm. But the general point of should this be in smart-contracts or smart-contract-extensions is a good question. I'm torn on it.

Additionally maybe we do not merge this until after v7. We don't have a deploy process figured for extensions yet..

[nfurfaro]

I think we should wait to merge till after v7.