WIP: qtdemux: Resuing stream when switching encryption status.

Instead of changing to a new caps that triggers a pipeline topology
change when transitioning from encrypted->clear or vice versa, force
qtdemux to create a new pad in these situations. The topology change is
not handled by decodebin2, even in theory, so we should not expect it
there. Decodebin3 is supposed to in theory handle this, but it currently
fails to do so (not investigated deeply, and I can't use decodebin3 in
my application yet for other reasons).
14 jobs for fix-caps-change-partial-encryption in 3 minutes and 26 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Preparation
passed #243432
gst indent

00:00:50

passed #243431
manifest

00:00:24

 
  Build
failed #243433
build fedora x86_64

00:02:34

failed #243434
build nodebug fedora x86_64

00:02:30

 
  Test
skipped #243435
check fedora
skipped #243436
integration testsuites fedora
 
  Full Builds
skipped #243438
build cerbero android universal
skipped #243439
build cerbero cross win32
skipped #243440
build cerbero cross win64
skipped #243437
build cerbero fedora x86_64
 
  Full Tests
skipped #243442
valgrind bad
skipped #243443
valgrind ges
skipped #243441
valgrind good
 
  Apps
skipped #243444
android universal examples
 
Name Stage Failure
failed
build fedora x86_64 Build
$ cd gst-build/
$ test -d build && find build -name '*.[ao]' -delete
$ rm -rf subprojects/*/.git/
$ rm -rf build/subprojects/*/.git/
Uploading artifacts...
manifest.xml: found 1 matching files
gst-build/: found 26093 matching files
Uploading artifacts to coordinator... ok id=243433 responseStatus=201 Created token=4ffxrAVV
ERROR: Job failed: exit code 1
failed
build nodebug fedora x86_64 Build
$ cd gst-build/
$ test -d build && find build -name '*.[ao]' -delete
$ rm -rf subprojects/*/.git/
$ rm -rf build/subprojects/*/.git/
Uploading artifacts...
manifest.xml: found 1 matching files
gst-build/: found 26093 matching files
Uploading artifacts to coordinator... ok id=243434 responseStatus=201 Created token=mSE_sbhD
ERROR: Job failed: exit code 1