Grab bag refactor

[jssblck]

Overview

Adds some stuff that would have been helpful to have when working on Sherlock, and I'm running into with Sparkle again.

• Refactors to more fully separate the different types of locator.
• Isolates tests per locator type.
• Adds StrictLocator, which requires the revision component.
• Adds Ord, PartialOrd, and JSONSchema implementations to all public types.
• Adds special types for the components of a locator (Package, Revision, OrgId).
  • This is what forced a breaking change.
• Renames the project field to package field to reduce confusion between the term "project" and "package" (as in, "PackageLocator").

Acceptance criteria

We can:

• Require locators to have a revision.
• Order locators without manually converting them to strings.
• Inspect the schema for locators.

Testing plan

Automated tests.

Risks

Not risky.

References

Part of the Sparkle work.

Checklist

• I added tests for this PR's change (or explained in the PR description why tests don't make sense).

[spatten]

I have questions about the ordering function, so let's chat about those and then I can re-review and approve

[spatten]

Nice! I like the change to implement Ord for the individual parts of the Locator, and the name change to Package.