Be an AuthenticationProvider so connection passwords can be held in keystore

[gjsjohnmurray]

Connection passwords can either be stored as plaintext in the connection definition or else be prompted for every time you connect.

Become an AuthenticationProvider that can store passwords in the workstation keystore/keychain. This API arrived in VS Code 1.54.

I think this is better approach than the env-variables one suggested in #452.

[DaveParr]

@gjsjohnmurray thanks for taking on the feedback. Is this live right now?

If it's on the main current release I'll go and re-install the extension today :)

[gjsjohnmurray]

@DaveParr no it isn't implemented yet. When it is we will update this issue.

[gjsjohnmurray]

Today's 0.27.0 release of the main extension implements this, and the 0.5.0 release of the MySQL/MariaDB driver leverages the new capability.