Add support for Firestore TTL

[JU-2094]

Description

API change to add Firestore TTL support for the CLI.
The implementation of the design change is tracked at b/249528585

Scenarios Tested

User Journeys tested:

• Set and Unset TTL in an existing Field override.
• Set and Unset TTL in a new configuration file.
• Don't affect existing TTL policies created without the CLI for backward compatibility.
• See other TTL policies not present in the configuration file.
• Don't affect TTL policies if the ttl property is undefined. Only take effect when is explicitly set.
• Remove field overrides and TTL policies when the --force flag is used.
• Verify there's only 1 TTL per collection.
• Verify that existing behavior remains if not using new property.
• Verify the order of field overrides in the configuration file do not affect.
• Verify the type of the ttl property is enforced to be boolean.

[HansiMou]

LGTM from TTL backend.

[codecov-commenter]

Codecov Report

Base: 56.27% // Head: 56.27% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (b6762f9) compared to base (e984a6c).
Patch coverage: 38.70% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5267   +/-   ##
=======================================
  Coverage   56.27%   56.27%           
=======================================
  Files         309      310    +1     
  Lines       20820    20886   +66     
  Branches     4224     4244   +20     
=======================================
+ Hits        11716    11754   +38     
- Misses       8092     8112   +20     
- Partials     1012     1020    +8     

Impacted Files	Coverage Δ
src/firestore/indexes.ts	32.01% <10.52%> (-1.04%)	⬇️
src/firestore/validator.ts	80.95% <33.33%> (-7.94%)	⬇️
src/firestore/indexes-api.ts	100.00% <100.00%> (ø)
src/firestore/indexes-sort.ts	75.38% <100.00%> (+1.19%)	⬆️
src/firestore/util.ts	64.70% <100.00%> (+4.70%)	⬆️
src/emulator/auth/state.ts	84.87% <0.00%> (-0.57%)	⬇️
src/emulator/functionsEmulator.ts	7.06% <0.00%> (-0.03%)	⬇️
src/emulator/eventarcEmulatorUtils.ts	62.06% <0.00%> (ø)
src/utils.ts	67.46% <0.00%> (+0.34%)	⬆️
src/emulator/auth/server.ts	72.54% <0.00%> (+0.66%)	⬆️
... and 2 more

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