adding finders to composition and query planning

[clenfest]

Notes to reviewers:

• There are a couple of tests that I haven't yet written yet. Those are annotated with an it.todo and should be done shortly.
• There are still some TODOs in the code, mostly involving stuff that isn't going to make it into the GA version, but will be done at some point in the future. I'm guessing we may want another tag for this, but not sure what I should change it to.

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 65a12072628dfcc5d223bba2295a58aa298015ef

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[netlify[bot]]

✅ Deploy Preview for apollo-federation-docs canceled.

Name	Link
🔨 Latest commit	9ffeb7d075c49b7d0998e0ea3235c70feaeace5c
🔍 Latest deploy log	https://app.netlify.com/sites/apollo-federation-docs/deploys/63e1b00c22b93c00097d6571

[codesandbox-ci[bot]]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.