pbutils: Add audio, base and video library to Requires line in the pkg-config file

We use all those libraries internally and include headers from them in
the public headers.

And add the tag library to Requires.private as we use it internally and
it would be needed when doing static linking.

Fixes gstreamer/gst-plugins-base#537
10 jobs for <span class="ref-name">pbutils-pc</span> in 84 minutes and 35 seconds (queued for 8 minutes and 32 seconds)
Status Job ID Name Coverage
  Preparation
passed #79614
gst indent

00:00:52

passed #79613
manifest

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  Build
passed #79615
build fedora x86_64

00:07:39

 
  Test
passed #79616
check fedora

00:04:58

 
  Full Builds
passed #79617
build android arm64 api28

00:04:22

passed #79619
build cerbero cross win32

00:59:06

passed #79740
build cerbero cross win64

00:06:45

passed #79618
build cerbero fedora x86_64

00:50:11

failed #79620
build cerbero cross win64

01:00:00

passed #79735
build cerbero cross win64

00:07:38