window: Add search protocol filter

Users sometime wish to filter chat list by protocol,
which is useful if the list is too big.

GdTaggedEntry from libgd project is used for the entry.
7 jobs for wip/sadiq/tagged-search in 8 minutes and 54 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #367107
librem5
build-pureos-gcc-byzantium

00:01:59

 
  Test
passed #367109
librem5
check-po

00:00:19

passed #367108
librem5
test:debian-gcc

00:01:33

22.5%
 
  Package
passed #367110
librem5
package-pureos-byzantium

00:01:36

passed #367111
librem5:arm64
package-pureos-byzantium:arm64

00:05:20

 
  Test Package
passed #367112
librem5
autopkgtest-pureos-byzantium-package

00:01:06

passed #367113
librem5
lintian-pureos-byzantium-package

00:00:51