basesrc: Add public gst_base_src_negotiate () function

This is useful for when format changes occur mid-stream.
22 jobs for master in 41 minutes and 52 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Preparation
passed #380090
gst indent

00:00:34

passed #380089
manifest

00:00:31

 
  Build
passed #380096
build cerbero android universal

00:10:45

passed #380097
build cerbero cross win32

00:09:18

passed #380098
build cerbero cross win64

00:05:27

passed #380095
build cerbero fedora x86_64

00:10:52

manual #380100
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #380099
gst-macos-10.14
build cerbero macos x86_64

00:06:35

passed #380091
build fedora x86_64

00:11:51

passed #380092
build nodebug fedora x86_64

00:10:48

passed #380093
build static fedora x86_64

00:15:34

passed #380094
build static nodebug fedora x86_64

00:14:09

 
  Test
passed #380101
check fedora

00:03:25

passed #380102
integration testsuites fedora

00:15:06

passed #380107
valgrind bad

00:17:35

failed #380104
valgrind base

00:23:02

passed #380103
valgrind core

00:25:42

passed #380108
valgrind ges

00:07:02

passed #380105
valgrind good

00:13:34

passed #380106
valgrind ugly

00:02:09

 
  Integrate
skipped #380109
android universal examples
skipped #380110
documentation
 
Name Stage Failure
failed
valgrind base Test
           Total: 620
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 1314 matching files
Uploading artifacts to coordinator... ok id=380104 responseStatus=201 Created token=PfsyBpVa
Uploading artifacts...
validate-logs/*.xml: found 1 matching files
Uploading artifacts to coordinator... ok id=380104 responseStatus=201 Created token=PfsyBpVa
ERROR: Job failed: exit code 1