Tree-shakeable Target

[schmidt-sebastian]

This is the first step in making Query tree-shakeable (but has not side impact on its own, since the non tree-shakeable Query relies on all functionality).

This PR:

• Makes all Target methods tree-shakeable.
• Split up Target into Target/TargetImpl, which adds a lot of code and indirection, but hides the memoizedCanonicalId from the public API
• Updated ObjectMap to use the new equals functions instead of Equatable, which allows Targets to still be stored in Objects.
• Adds the ability to use the new equals methods in our custom test equals helper.

The diff is easier to review in IntelliJ (it correlates more of the existing code). In general, this PR only contains moved code and no logic modifications.

[google-oss-bot]

Binary Size Report

Affected SDKs

• @firebase/firestore

  Type	Base (e733228)	Head (c18b3ec)	Diff
  browser	249 kB	249 kB	+140 B (+0.1%)
  esm2017	194 kB	194 kB	+61 B (+0.0%)
  main	491 kB	492 kB	+989 B (+0.2%)
  module	246 kB	247 kB	+164 B (+0.1%)

• @firebase/firestore/lite

  Type	Base (e733228)	Head (c18b3ec)	Diff
  main	139 kB	140 kB	+570 B (+0.4%)

• @firebase/firestore/memory

  Type	Base (e733228)	Head (c18b3ec)	Diff
  browser	186 kB	186 kB	+174 B (+0.1%)
  esm2017	145 kB	145 kB	+66 B (+0.0%)
  main	361 kB	362 kB	+943 B (+0.3%)
  module	184 kB	184 kB	+150 B (+0.1%)

• firebase

  Type	Base (e733228)	Head (c18b3ec)	Diff
  firebase-firestore.js	287 kB	287 kB	+143 B (+0.0%)
  firebase-firestore.memory.js	226 kB	226 kB	+152 B (+0.1%)
  firebase.js	820 kB	820 kB	+144 B (+0.0%)

Test Logs

• Base (e7332282): https://github.com/firebase/firebase-js-sdk/actions/runs/142134300
• Head (c18b3ec5): https://github.com/firebase/firebase-js-sdk/actions/runs/143875506