Fix: Cannot choose reader topics in some languages

[ashiagr]

Fixes #16237

This PR fixes a bug where a valid URL encoded tag with % symbols was sanitized to remove % symbols making it an invalid URL encoded tag and causing issues in following the tag.

See #16237 (comment) for more details.

/cc @thehenrybyrd

To test:

Test.1 - Follow/ unfollow a topic in a language like Chinese (Taiwan)

1. Head to Reader > ⚙️ > Followed Topics and unfollow any topics you currently follow. (Alternatively, login to an account with no followed topics)
2. Head to My Site > Me > App Settings and change Interface Language to a language reported in the linked issue such as Chinese (Taiwan).
3. Back in Reader, choose the Discover tab (second tab from the left), and tap the "Get Started" button (the blue button in the middle of the tab when no topics are followed).
4. Select a few topics and tap the button at the bottom.
5. Note that the topics are followed.
6. Unfollow a topic.
7. Note that the topic is unfollowed.

device-2022-06-22-111733.mp4

Test.2 - Add a topic with invalid characters

1. On the Reader tab, tap on the Setting menu (⚙️ icon) on the top to open "Manage Topics & Sites" screen.
2. Add a tag with invalid characters on "Manage Topics & Sites" screen.
3. Notice a toast is shown that the tag is invalid.

device-2022-06-22-112316.mp4

Test.3 - Add a topic with spaces

1. On the Reader tab, tap on the Setting menu (⚙️ icon) on the top to open "Manage Topics & Sites" screen.
2. Add a tag with spaces on "Manage Topics & Sites" screen.
3. Notice that the tag is sanitized with dashes and followed.

device-2022-06-22-113057.mp4

Regression Notes

1. Potential unintended areas of impact
   Strings that are not URL encoded should be sanitized with dashes.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Tested manually. See "To test" section.

3. What automated tests I added (or what prevented me from doing so)
   Added string sanitization tests in ReaderUtilsTest.

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.

[wpmobilebot]

You can test the WordPress changes on this Pull Request by downloading an installable build (wordpress-installable-build-pr16789-2a2eac3.apk), or scanning this QR code:

[wpmobilebot]

You can test the Jetpack changes on this Pull Request by downloading an installable build (jetpack-installable-build-pr16789-2a2eac3.apk), or scanning this QR code:

[zwarm]

@ashiagr - Nice use of URI 👍 Works as expected in Jetpack & WordPress.