Add access token revoke request to SDK

[bbirman]

No description provided.

[bbirman]

The currentUser default is here and in the signature so Swift can call it without providing an argument like: 
RestClient.shared.requestForRevokeAccessToken()


and obj-c can call with nil:
[[SFRestAPI sharedInstance] requestForRevokeAccessTokenWithUser:nil]

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^18 Test Results	586 ran	584 ✅		2 ❌

Test	Result
SalesforceSDKCore iOS ^18 Test Results
DomainDiscoveryCoordinatorTests.testCallbackSuccess()	❌ failure
SFUserAccountManagerTests.testUserAccountEncoding	❌ failure

• View SalesforceSDKCore iOS ^18 Test Results

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 61.68%. Comparing base (9f1264e) to head (a44dfc2).
⚠️ Report is 7 commits behind head on dev.

Files with missing lines	Patch %	Lines
...esforceSDKCore/Classes/Extensions/RestClient.swift	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #3964      +/-   ##
==========================================
+ Coverage   61.37%   61.68%   +0.31%     
==========================================
  Files         255      255              
  Lines       22722    22733      +11     
==========================================
+ Hits        13945    14023      +78     
+ Misses       8777     8710      -67     

Components	Coverage Δ
Analytics	70.78% <ø> (ø)
Common	70.23% <ø> (ø)
Core	51.83% <90.90%> (+0.49%)	⬆️
SmartStore	73.99% <ø> (ø)
MobileSync	87.41% <ø> (ø)

Files with missing lines	Coverage Δ
...esforceSDKCore/Classes/Extensions/RestClient.swift	82.01% <90.90%> (+5.45%)	⬆️

... and 8 files with indirect coverage changes

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[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^26 Test Results	586 ran	584 ✅		2 ❌

Test	Result
SalesforceSDKCore iOS ^26 Test Results
BootConfigPickerViewControllerTests.testBootConfigPickerViewRendered()	❌ failure
DomainDiscoveryCoordinatorTests.testExtraQueryParameters()	❌ failure

• View SalesforceSDKCore iOS ^26 Test Results