Inherit 'sieve-mode' faces from 'font-lock'

Inherit 'sieve-mode' faces from 'font-lock'

These Sieve faces were already a close mapping onto the Font Lock
ones, so this should usually look the same to users with the default
theme.  However, this makes it easier to theme these faces (just
define the usual 'font-lock-*-face' colors you want) and also fixes a
few edge cases (bug#62370).

* lisp/net/sieve-mode.el (sieve-control-commands)
(sieve-action-commands, sieve-test-commands, sieve-tagged-arguments):
Inherit from 'font-lock' faces.