glib2: split package into separate libraries

glib2: split package into separate libraries

Existing package contains five libraries, some of which are > 1MB. Allow
packages which depend on only some of them to only pull in the ones they
need by splitting this package into finer-grained packages. Transition
can be done piecemeal as depending on glib2 will still pull in all the
libraries.

The original split commit (6bb0d6bd2) had a typo: the glib2 meta-package
used 'DEPENDS:+glib2-gthread +glib2-gio' (missing '='), which caused
the meta-package to have no effective dependencies. This meant packages
declaring '+glib2' did not get the sub-packages installed, causing APK
dependency checks to fail for all glib2 libraries across ~60 packages.

This re-applies the split with 'DEPENDS:=+glib2-gthread +glib2-gio'
(correct assignment syntax), so the meta-package properly pulls in all
sub-packages for consumers that still declare '+glib2'.

Signed-off-by: Alexandru Ardelean <redacted>
Signed-off-by: Alexandru Ardelean <redacted>