feat: add spritesheet samples and tests

[irataxy]

b:181782257

• 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 2 region tags.

• media/transcoder/src/main/java/com/example/transcoder/CreateJobWithPeriodicImagesSpritesheet.java:19, tag transcoder_create_job_with_periodic_images_spritesheet
• media/transcoder/src/main/java/com/example/transcoder/CreateJobWithSetNumberImagesSpritesheet.java:19, tag transcoder_create_job_with_set_number_images_spritesheet

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