Improve Bitwarden integration

[PalmerAL]

This PR attempts to fix a few of the most common issues with the Bitwarden integration:

• Bitwarden recently started requiring an API key instead of a password in some cases: https://bitwarden.com/help/article/cli-auth-challenges/, which I believe is the cause of the recent issues about Bitwarden setup failing. This PR updates the installation flow to ask for a client ID and key instead of a username and password. This also makes it possible to connect Bitwarden accounts that have 2FA enabled.

Fixes #1796, #1394, #929

• Added a re-prompt for authentication if the user is signed out and tries to autofill a password. Previously, the authentication prompt would never show after setup was complete, which meant it was possible to end up in a state where you weren't signed in and there was no way to sign in again in the UI. This should hopefully fix Password Manager Issue #1689.

[aiyagari]

@PalmerAL I have revisited this with the latest release 1.24 to see if it is fixed. I entered the API key in the new dialog box as requested, and found the following:

• On nytimes.com it works
• On schwab.com it does not work
  On both sites, it does put the "key" icon on the field, so it is recognized as a login field by the browser. Somehow on one of the sites it is just not getting filled in.
  This is actually just an example - I find it working on 50% of sites overall.

[PalmerAL]

@aiyagari Thanks for letting me know - fixed in 2d1a3d7. If you see other sites where it's not working, please file issues for them!