Fixes AB#3429389 cleanup + optimized saveAndLoadAggregatedAccountData that identifies … (#2832)

Fixes
[AB#3429389](https://identitydivision.visualstudio.com/fac9d424-53d2-45c0-91b5-ef6ba7a6bf26/_workitems/edit/3429389)

This PR cleans up unused classes and methods that have not been used and
have been deprecated for the last 3 years.

It adds an optimized saveAndLoadAggregatedAccount() method that
identifies the targetCache, on which save() and
loadAggregatedAccountData() methods should be called, once. The current
SaveAndLoadAggregatedAccount() method performs 2 disjoint operations -
1. save() -> finds the token cache (FOCI or ProcessUId), save the
accounts and credentials to the cache. 2. loadAggregatedAccountData ->
finds the token cache again (by querying metadata from the storage and
performing multiple operations) and then, loading the aggregated account
data.
This PR gets rid of the duplicate 'finding the token cache' part.

---------

Co-authored-by: Copilot <[email protected]>

Author: siddhijain

changelog.txt

@@ -1,5 +1,6 @@
 vNext
 ----------
+- [MINOR] Add optimized saveAndLoadAggregatedAccountData method in BrokerOAuth2TokenCache (#2832)
 - [MINOR] Remove MavenCentral repository from build.gradle files (#2830)
 - [MINOR] Determine whether broker app opts out from battery optimization (#2819)
 - [MINOR] Cache Active Broker In Memory (BrokerDiscoveryClient) (#2817)