Issue/14299 add payload to fetch sites wp module

[ashiagr]

Issue: #14299

This PR adds an empty FetchSitesPayload to newFetchSitesAction as part of the Jetpack app filters support in the fetch sites API.

Related PRs:
wordpress-mobile/WordPress-FluxC-Android#1936
#14356

To test:

• Launch and login to app
• Go to My Sites tab
• Notice that all sites for the user are shown on the Site Picker

Merge Instructions:

• Make sure Filter Jetpack sites for Jetpack app WordPress-FluxC-Android#1936 is merged to FluxC develop
• Create tag on FluxC develop
• Update FluxC tag in build.gradle in this PR
• Remove Not Ready for Merge label
• Merge this PR with develop

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

Messages

📖

This PR contains changes in the subtree libs/login/. It is your responsibility to ensure these changes are merged back into wordpress-mobile/WordPress-Login-Flow-Android. Follow these handy steps! WARNING: Make sure your git version is 2.19.x or lower - there is currently a bug in later versions that will corrupt the subtree history! cd WordPress-Android git checkout issue/14299-add-payload-to-fetch-sites-wp-module git subtree push --prefix=libs/login/ https://github.com/wordpress-mobile/WordPress-Login-Flow-Android.git merge/WordPress-Android/14397 Browse to https://github.com/wordpress-mobile/WordPress-Login-Flow-Android/pull/new/merge/WordPress-Android/14397 and open a new PR.

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[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APK here.

[ParaskP7]

👋 @ashiagr !

I have reviewed and tested this PR as per the instructions, everything looks as expected, good job! 🌟

PS: As per your merge instruction we need to create a FluxC tag before merging.