Fix (mostly multibyte) issues in sieve-manage.el (Bug#54154)

Fix (mostly multibyte) issues in sieve-manage.el (Bug#54154)

The managesieve protocol (s. RFC5804) requires support for (a sightly
restricted variant of) UTF-8 in script content and script names. This
commit fixes/improves the handling of multibyte characters.

In addition, `sieve-manage-getscript' now properly handles NO
responses from the server instead of inflooping.

There are also some logging improvements.

* lisp/net/sieve-manage.el
(sieve-manage--append-to-log):
(sieve-manage--message):
(sieve-manage--error):
(sieve-manage-encode):
(sieve-manage-decode):
(sieve-manage-no-p): New functions.
(sieve-manage-make-process-buffer): Switch process buffer to unibyte.
(sieve-manage-open-server): Add `:coding 'raw-text-unix` to
`open-network-stream' call. Use unix EOLs in order to keep matching
CRLF (aka "\r\n") intact.
(sieve-manage-send): Make sure that UTF-8 multibyte characters are
properly encoded before sending data to the server.
(sieve-manage-getscript):
(sieve-manage-putscript): Use the changes above to fix down/uploading
scripts containing UTF-8 multibyte characters.
(sieve-manage-listscripts):
(sieve-manage-havespace)
(sieve-manage-getscript)
(sieve-manage-putscript):
(sieve-manage-deletescript):
(sieve-manage-setactive): Use the changes above to fix handling of
script names which contain UTF-8 multibyte characters.
(sieve-manage-parse-string):
(sieve-manage-getscript): Add handling of server responses with type
NO. Abort `sieve-manage-getscript' and show error message in message
area.
(sieve-manage-erase):
(sieve-manage-drop-next-answer):
(sieve-manage-parse-crlf): Return erased/dropped data (instead of nil).
(sieve-sasl-auth):
(sieve-manage-getscript):
(sieve-manage-erase):
(sieve-manage-open-server):
(sieve-manage-open):
(sieve-manage-send): Improve logging.