bug#62370: 28.1; sieve-mode: faces should inherit from font-lock-X-face faces

[Trent W. Buck]

sieve-mode as at Emacs 28.1 defines its colors ab initio.
This means they have to be themed by hand.
I think sieve-mode should inherit from font-lock-*-face,
as most other things do.

Here is a quick-and-dirty version I knocked out for personal use:

    (custom-set-faces
     '(sieve-control-commands ((t :inherit font-lock-builtin-face)))
     '(sieve-action-commands  ((t :inherit font-lock-function-name-face)))
     '(sieve-test-commands    ((t :inherit font-lock-variable-name-face)))
     '(sieve-tagged-arguments ((t :inherit font-lock-type-face))))

Screenshot from 2023-03-22 16-23-48.png
Description: before.png

Screenshot from 2023-03-22 16-40-15.png
Description: after.png