cryptsetup: allow customizing cache behavior

cryptsetup: allow customizing cache behavior

The new "password-cache" option allows customizing behavior of the
ask-password module in regards to caching credentials in the kernel
keyring. There are 3 possible values for this option:
  * read-only - look for credentials in kernel keyring before asking
  * on - same as read-only, but also save credentials input by user
  * off - disable keyring credential cache

Currently the cache is forced upon the user and this can cause issues.
For example, if user wants to attach two volumes with two different
FIDO2 tokens in a quick succession, the attachment operation for the
second volume will use the PIN cached from the first FIDO2 token, which
of course will fail and since tokens are only attempted once, this will
cause fallback to a password prompt.