Feat: profile edit main settings part one

What does this MR do and why?

• This s a splitted partial of !143932 (closed).
• This MR implements updating username/email/pronouns/pronunciation feature in Vue implementation.

Feat: profile edit main settings part one

• Add a main settings component for main settings.
• Add a password prompt modal to profile edit component for verification.
• Enhance profile_helper for providing data needed by frontend.
• Add tests against these changes above.

Changlog: changed EE: true

Related to #389918, #393769

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

The section in the red rectangle is the UI changes in this MR.

Before submitting

Submitting with email changed

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable feature flag with following code in Rails Console

 Feature.enable(:profile_edit_vue)

2. Click on the current user avatar > Edit profile