Localhost mode updates for SDK_READY_FROM_CACHE

[EmilianoSanchez]

JS SDK

What did you accomplish?

• Updated localhost mode to support LocalStorage and emit SDK_READY_FROM_CACHE event.
  • As in online mode, clients emit SDK_READY_FROM_CACHE event before SDK_READY. If new clients are created after the event has been emitted, they not emit it again but can evaluate splits from cache.
  • Unlike online mode, when using LocalStorage clients always emit SDK_READY_FROM_CACHE, even the first time when there is not cached data.
• Fixed traffic type value of mocked splits to 'localhost'.

How do we test the changes introduced in this PR?

• Updated and added new asserts to E2E tests.

Extra Notes

[sonarqube-pull-requests]

SonarQube Quality Gate

0.0% Coverage on New Code (is less than 80%)

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