Add API for setting icon on ScreenLock screen

[bbirman]

Sample code usage:

        let screenLockConfig = ScreenLockUIConfiguration()
        screenLockConfig.icon = [generated icon]
        SalesforceManager.shared.screenLock().configuration = screenLockConfig

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^26 Test Results	634 ran	629 ✅		5 ❌

Test	Result
SalesforceSDKCore iOS ^26 Test Results
testExtraQueryParameters()	❌ failure
SFSDKAuthConfigUtilTests.testBrowserBasedLoginEnabled	❌ failure
SalesforceRestAPITests.testCreateQuerySearchDelete	❌ failure
SalesforceRestAPITests.testUploadOwnedFilesDelete	❌ failure
SalesforceRestAPITests.testUploadShareFileSharesSharedFilesUnshareDelete	❌ failure

• View SalesforceSDKCore iOS ^26 Test Results

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^18 Test Results	634 ran	627 ✅		7 ❌

Test	Result
SalesforceSDKCore iOS ^18 Test Results
testMalformedCallbackURL()	❌ failure
SFSDKAuthConfigUtilTests.testBrowserBasedLoginEnabled	❌ failure
SFUserAccountManagerTests.testUserAccountEncoding	❌ failure
SalesforceRestAPITests.testCreateQuerySearchDelete	❌ failure
SalesforceRestAPITests.testUpdateWithIfUnmodifiedSince	❌ failure
SalesforceRestAPITests.testUploadOwnedFilesDelete	❌ failure
SalesforceRestAPITests.testUploadShareFileSharesSharedFilesUnshareDelete	❌ failure

• View SalesforceSDKCore iOS ^18 Test Results

[github-actions]

	Tests	Passed ✅	Skipped	Failed
AuthFlowTester UI Test Results all	1 ran	1 ✅

Test	Result
No test annotations available

• View AuthFlowTester UI Test Results all

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.18%. Comparing base (b7b5475) to head (544894c).
⚠️ Report is 13 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #4045      +/-   ##
==========================================
+ Coverage   68.15%   68.18%   +0.03%     
==========================================
  Files         245      246       +1     
  Lines       21461    21471      +10     
==========================================
+ Hits        14626    14641      +15     
+ Misses       6835     6830       -5     

Components	Coverage Δ
Analytics	70.78% <ø> (ø)
Common	70.69% <ø> (ø)
Core	61.65% <100.00%> (+0.06%)	⬆️
SmartStore	73.44% <ø> (ø)
MobileSync	88.79% <ø> (ø)

Files with missing lines	Coverage Δ
...ecurity/ScreenLock/ScreenLockManagerInternal.swift	62.79% <100.00%> (+0.29%)	⬆️
...ecurity/ScreenLock/ScreenLockUIConfiguration.swift	100.00% <100.00%> (ø)
...Classes/Security/ScreenLock/ScreenLockUIView.swift	52.11% <100.00%> (-0.92%)	⬇️

... and 4 files with indirect coverage changes

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