[Payment Method Improvements] Remove Feature Flag and related old code

[backwardstruck]

Closes: #11625

Description

This PR removes the feature flag and related old code pertaining to cash payments. Specifically, it removes the OtherPaymentMethodsEnabled class as well as all deprecated cash collection code, including dialogs and associated tests. These changes are required to clean up the codebase and prepare for the next release, ensuring that only relevant and up-to-date code remains.

Steps to reproduce

1. Run the app and navigate to the select payment method screen when paying for an open order.
2. Select "Cash"
3. Ensure that no remnants of the "OtherPaymentMethodsEnabled" class or related cash collection code are present.
4. Verify that the functionality aligns with the expectations and no deprecated dialogs appear.

Testing information

Devices Used

• Tablet emulator
• Physical device

Testing Scenarios

• Confirm the removal of the feature flag and related classes from the codebase.
• Ensure all tests pass and no deprecated dialogs are shown during payment method selection.

Areas Not Tested

• Backend functionality related to payment processing, which is outside the scope of this PR.

Images/gif

N/A

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

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Feel free to adjust any specific parts as needed!

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Flavor	Jalapeno
	Build Type	Debug
	Commit	b37318b
	Direct Download	woocommerce-prototype-build-pr11652-b37318b.apk

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 40.25%. Comparing base (f040b34) to head (b37318b).

Files	Patch %	Lines
...ts/methodselection/SelectPaymentMethodViewModel.kt	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk   #11652   +/-   ##
=========================================
  Coverage     40.24%   40.25%           
+ Complexity     5331     5329    -2     
=========================================
  Files          1132     1131    -1     
  Lines         65288    65267   -21     
  Branches       9056     9052    -4     
=========================================
- Hits          26273    26271    -2     
+ Misses        36594    36576   -18     
+ Partials       2421     2420    -1     

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[kidinov]

LGTM!