Use KDS for buttons in accounts application

[MisRob]

Please check KDS guidelines on buttons and links and use KDS components (you may need KButton or KRouterLink) instead of Vuetify's VBtn in the following places of the accounts app (frontend/accounts):

(1) "Sign in" and "Create an account" on the sign-in page

(2) "Finish" on the registration page

(3) "Continue to sign-in page" on the activation link sent page

(4) "Continue to sign-in" on the account created page

(5) "Request a new activation link" and "Continue to sign-in page" on the account not activated page

(6) "Request a new activation link" and "Continue to sign-in page" on the activation failed page

(7) "Submit" and "Continue to sign-in page" on the request new activation link page

(8) "Continue to sign-in page" on the activation link resent page

(9) "Submit" and "Continue to sign-in page" on the forgot password page

(10) "Continue to sign-in page" on the password reset sent page

(11) "Submit" and "Continue to sign-in page" on the reset password page

(12) "Continue to sign-in page" on the password reset success page

(13) "Request a new password reset link" and "Continue to sign-in page" on the reset expired page

(14) "Continue to sign-in page" on the account deleted page

Additional information

• It will make sense to address this issue in one PR because many /accounts pages are built around one component, MessageLayout, that needs to be updated
• There are some inconsistencies that need to be unified - for example, see (3) and (4) where two different strings are used to describe the same action - "Continue to sign-in page" and "Continue to sign-in". Also, their appearance is a link on one page and a button on another. Please check also other screenshots in this regard.
• ActionLink (a wrapper around Vuetify's VBtn) in MessageLayout will need to be removed in favor of a KDS component as part of this issue. However, ActionLink contains some extra functionality. Part of this task is to check if some of it needs to be transferred to KDS API, or if we can use KDS as is. That makes this task potentially more complex.
  Note: We don't want to remove ActionLink component itself as part of this issue because it is used from many other places in the app. It is rather to replace it with KDS components in MessageLayout. That said, it would be good to make some notes about pitfalls of replacing ActionLink with KDS components so we can use it when dropping ActionLinks in the rest of the app.

Workflows affected

• Sign-in
• Registration
• Password reset
• Account deletion

[bjester]

Closed by #3891