Deprecate GRegex

GRegex is based off of PCRE1, and cannot be moved to PCRE2 without
breaking its API contract. PCRE1 is in maintenance mode, and will not
see any new feature.

GRegex made sense back in the day when we embedded a copy of PCRE, but:

 - the maintenance burden required to update the copy of PCRE to keep up
   with upstream, coupled with the lack of synchronisation between GLib
   and PCRE releases, has become too high
 - downstream distributors try very hard to not rely on vendored
   dependencies, which meant that GLib depended on a system copy of PCRE
   anyway, except on certain platforms, which made for interesting bugs
 - regular expressions are a niche use case, and PCRE is already
   portable to all the platforms GLib cares about

Thus, we recommend users to migrate their code from GRegex to PCRE2.

Fixes: #1085
17 jobs for no-more-regex in 71 minutes and 15 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Style Check
passed #705984
check-todos

00:01:28

failed #705983
allowed to fail
style-check-diff

00:01:44

 
  Build
passed #705989
cross-android_api21_arm64

00:04:24

passed #705990
cross-android_api28_arm64

00:03:41

passed #705991
cross-mingw64

00:02:23

passed #705986
debian-stable-x86_64

00:04:04

passed #705985
fedora-x86_64

00:17:15

passed #705994
freebsd-11
freebsd-11-x86_64

00:05:48

passed #705995
freebsd-12
freebsd-12-x86_64

00:05:13

passed #705988
G_DISABLE_ASSERT

00:05:23

passed #705987
installed-tests

00:09:39

passed #705996
macos
macos

00:03:53

passed #705992
win32-ps
msys2-mingw32

00:10:46

passed #705993
win32-ps
vs2017-x64

00:08:10

 
  Coverage
passed #705997
coverage

00:02:08

78.1%
 
  Analysis
passed #705999
scan-build

00:22:04

failed #705998
allowed to fail
valgrind

00:27:24

 
Name Stage Failure
failed
valgrind Analysis
Uploading artifacts...
_build/config.h: found 1 matching files

_build/glib/glibconfig.h: found 1 matching files

_build/meson-logs: found 7 matching files

Uploading artifacts to coordinator... ok
id=705998 responseStatus=201 Created token=xF3-TVhc
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=705998 responseStatus=201 Created token=xF3-TVhc
ERROR: Job failed: exit code 1
failed
style-check-diff Style Check
 						 gpointer          user_data);

-
GLIB_DEPRECATED_IN_2_66
GRegex *g_regex_new (const gchar *pattern,
GRegexCompileFlags compile_options,
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1