feat(livestream): add VOD clip samples and test

[irataxy]

Description

Fixes b:341726237

Important: FFmpeg (https://www.ffmpeg.org/) must be installed in the test environment.

sudo apt install ffmpeg

Will update the other samples to the latest sample guidelines in a follow up PR.

Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 4 region tags.

• media/livestream/src/main/java/com/example/livestream/CreateChannelClip.java:19, tag livestream_create_channel_clip
• media/livestream/src/main/java/com/example/livestream/DeleteChannelClip.java:19, tag livestream_delete_channel_clip
• media/livestream/src/main/java/com/example/livestream/GetChannelClip.java:19, tag livestream_get_channel_clip
• media/livestream/src/main/java/com/example/livestream/ListChannelClips.java:19, tag livestream_list_channel_clips

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