Add /.well-known/change-password redirect

[swissspidy]

Spec: ​https://w3c.github.io/webappsec-change-password-url/
Related core ticket: ​https://core.trac.wordpress.org/ticket/51173

While the best approach for core itself is still being discussed there, I figured that for meta this could be done independently without any dependency on the core change.

https://wordpress.org/.well-known/change-password could redirect to https://wordpress.org/support/users/<username>/edit/

[dd32]

In 11330:

Add support for ​https://wordpress.org/.well-known/change-password as supported by Safari, Chrome, and 1Password.

Introduces ​https://wordpress.org/support/users/my-profile/ to make redirects to the current users profile (and prompt for login otherwise).

Fixes #5830.

[dd32]

In 11331:

Add a missing exit; missed in [11330].

See #5830.

[dd32]

In 11333:

Support: Use https://wordpress.org/support/users/profile/edit/ to direct to the current users profile, to match the existing ​https://profiles.wordpress.org/profile/ shortcut.

Ammends [11330].
See #5830.

[dd32]

In 11335:

Support: Make the https://wordpress.org/support/users/profile/edit/ url work when logged out.

Previously broken in [11333].
See #5830.