track: Avoid various sorting operations before timeline commit

These are showing up in performance profile of 1000+ clips looped addition.
All this is done at commit time as well, so let that do only one update and
sorting.
13 jobs for add-clip-perf-step1 in 39 minutes and 38 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Preparation
passed #244989
gst indent

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passed #244988
manifest

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  Build
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build fedora x86_64

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passed #244991
build nodebug fedora x86_64

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  Test
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check fedora

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passed #244993
integration testsuites fedora

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  Full Builds
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build cerbero android universal

00:10:45

passed #244996
build cerbero cross win32

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passed #244997
build cerbero cross win64

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passed #244994
build cerbero fedora x86_64

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  Full Tests
passed #245107
valgrind ges

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failed #244998
valgrind ges

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  Apps
passed #244999
android universal examples

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