Create SnapshotsPreviewRuntimeRetentionTransform to change Previews to runtime retention

[rbro112]

Creates an instrumentation/transform that finds all Preview/Preview.Container (repeatable) annotations and forces them to be runtime visible. This is a workaround to https://issuetracker.google.com/issues/168524920, as D8 will unexpectedly strip Binary/Class annotations.

Also:

• adds debugOptions and the ability to force invalidate a transform using a system time to make sure transforms aren't cached (taken from here).
• Adds snapshots.experimentalTransformEnabled which can act as an opt-in to this behavior until we've fully tested and are ready for 1.0

[rbro112]

• Remove deprecated fields #145
• Remove snapshots-processor and all KSP-related dependencies/references #148
• Remove KSP and make experimentalTransformEnabled default #141
• Remove KSP and use new transform in sample #140
• Create SnapshotsPreviewRuntimeRetentionTransform to change Previews to runtime retention #139 👈
• Reflectively invoking composables pt 1 - SDK #123 : 2 other dependent PRs (#124 , #137 )
• main

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[trevor-e]

What's the need for this? Does the other override fun visitAnnotation() not cover all cases?

[rbro112]

Nope, that will only cover the annotations on the class-level. We need a separate method visitor to visit the annotations on each method, which is what this is doing.

Without this, we'd just be marking class-level Preview annotations as runtime, instead of class and method level which is what we want.

The class annotation visitor handles multipreview annotation classes that have the preview annotation, and the method annotation visitor handles actual preview methods annotated with Preview.