Add experimental API for seeking Transitions

Bug: 259291539
Bug: 259291404

Relnote: "Add SeekableTransitionState to allow developers to
control the progress of a transition."

Test: new tests, manual test using sample

Change-Id: I8e69df11beeb580c8ba4552fc5d7647367a44dcc

• compose/animation/animation-core/api/current.txt[diff]
• compose/animation/animation-core/api/restricted_current.txt[diff]
• compose/animation/animation-core/samples/build.gradle[diff]
• compose/animation/animation-core/samples/src/main/java/androidx/compose/animation/core/samples/TransitionSamples.kt[diff]
• compose/animation/animation-core/src/androidAndroidTest/kotlin/androidx/compose/animation/core/SeekableTransitionStateTest.kt[Added - diff]
• compose/animation/animation-core/src/commonMain/kotlin/androidx/compose/animation/core/Animation.kt[diff]
• compose/animation/animation-core/src/commonMain/kotlin/androidx/compose/animation/core/Transition.kt[diff]
• compose/animation/animation/integration-tests/animation-demos/src/main/java/androidx/compose/animation/demos/AnimationDemos.kt[diff]