Add Login for Admin feature

[brandonpage]

The Android implementation of this feature is quite a bit more involved and far reaching than its iOS counterpart. I choose to do a mini re-write of how the LoginViewModel handles generating urls because:

• loginUrl, browserCustomTabUrl, the authorization url used for token migration and the authorization url used for front door bridge were all created from a single function that retuned a single url. With the Web Server flow, running that function a second time generates a new code verifier and will break login using any previously generated url. I foresee future scenarios where this becomes very problematic if we are starting and cancelling/switching different auth flows.
• With BrowserCustomTabUrlSource it was possible to generate an authorization url for singleServerCustomTabActivity that did not use the Web Server Flow, which should never be allowed.
• Adding another boolean flag (like I did on iOS) doubles the matrix of test scenarios and makes the code harder to follow. This PR aims to do the opposite, removing several instances of if (!sdkManager.isBrowserLoginEnabled && !singleServerCustomTabActivity && !viewModel.isUsingFrontDoorBridge ... .

To address the above issues, this PR:

• Changes getAuthorizationUrl to generateAuthorizationUrl (maybe it should be plural?), which sets both loginUrl and browserCustomTabUrl and returns nothing.
• Add a generateMigrationAuthorizationPath function to handle Token Migration Authorization Url generation separately.
• Add a separate frontDoorBridgeUrl variable so loginUrl never needs to be re-generated to avoid using Web Server.
• Add a new (very simple) onBrowserCustomTabReady launching mechanism.

Demo of cancelling 'Login for Admin' vs org triggered Advanced Auth:

login_for_admin_cancel.mp4

[github-actions]

	1 Warning
⚠️	Big PR, try to keep changes smaller if you can.

Generated by 🚫 Danger

[JohnsonEricAtSalesforce]

👍🏻

[codecov]

Codecov Report

❌ Patch coverage is 83.05085% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.89%. Comparing base (5122b1b) to head (3df1c5a).
⚠️ Report is 3 commits behind head on dev.

Files with missing lines	Patch %	Lines
...src/com/salesforce/androidsdk/ui/LoginViewModel.kt	85.71%	4 Missing and 8 partials ⚠️
.../src/com/salesforce/androidsdk/ui/LoginActivity.kt	78.94%	0 Missing and 4 partials ⚠️
...m/salesforce/androidsdk/ui/components/LoginView.kt	71.42%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #2870      +/-   ##
============================================
- Coverage     64.90%   64.89%   -0.02%     
- Complexity     2974     2979       +5     
============================================
  Files           222      222              
  Lines         17449    17489      +40     
  Branches       2489     2496       +7     
============================================
+ Hits          11325    11349      +24     
- Misses         4920     4926       +6     
- Partials       1204     1214      +10     

Components	Coverage Δ
Analytics	47.92% <ø> (ø)
SalesforceSDK	59.83% <83.05%> (+<0.01%)	⬆️
Hybrid	59.05% <ø> (ø)
SmartStore	78.20% <ø> (ø)
MobileSync	81.68% <ø> (ø)
React	51.50% <ø> (ø)

Files with missing lines	Coverage Δ
...salesforce/androidsdk/ui/TokenMigrationActivity.kt	83.60% <100.00%> (-0.14%)	⬇️
.../src/com/salesforce/androidsdk/ui/LoginActivity.kt	43.67% <78.94%> (-1.54%)	⬇️
...m/salesforce/androidsdk/ui/components/LoginView.kt	44.70% <71.42%> (+0.99%)	⬆️
...src/com/salesforce/androidsdk/ui/LoginViewModel.kt	87.91% <85.71%> (-0.71%)	⬇️

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