[dvc][server][controller][router] Removed Optional from Store API

[FelixGV]

The Store::getVersion API used to return an Optional<Version>, now it instead returns a @Nullable Version. Also added a getVersionOrThrow API which can throw StoreVersionNotFoundException, a new exception type.

Lots of refactoring to adapt to the change, though these should be non-functional changes.

Significant changes:

• Some usages of getVersion in the consumer client were doing naked .get() so these have been replaced by getVersionOrThrow.

• Refactored the HelixCustomizedViewOfflinePushRepository to make all changes to the resourceToPartitionCountMap go through fewer private functions, and fixed some naked .get() bug there as well.

Miscellaneous main code changes:

• Deleted the ExpiringSet and its usage in ReadQuotaEnforcementHandler.

Miscellaneous test code changes:

• Removed nearly all mocking of the deprecated function PubSubProducerAdapter::getNumberOfPartitions and replaced it with VeniceWriterOptions::setPartitionCount.

• Added timeouts to all TestVeniceHelixAdminWithSharedEnvironment tests.

• Added the ability to override the duration of some long operations in HelixReadOnlySchemaRepository and PubSubConstants, only for tests. This reduces venice-common unit tests by ~6 minutes.

How was this PR tested?

GHCI.

Does this PR introduce any user-facing changes?

• [x] No. You can skip the rest of this section.
• [ ] Yes. Make sure to explain your proposed changes and call out the behavior change.