This removes the need to calculate the time needed to run the doSomeWork
method. Consequently, we can use both the real Clock/Handler and the
FakeClock without changing the way the playback loop works and without
violating the interfaces of Clock or Handler.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=180665647

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=180558741

Especially this removes the need for the Clock interface to directly
implement Handler methods. Instead, we have a separate Handler interface
and the FakeClock is able to construct such a Handler.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=179918255

The default implementation is just calling through to handler.postDelayed,
while the fake clock uses its internal time value to trigger the handler
calls at the correct time.

This is useful to apply a fake clock in situations where a handler is used to
post delayed messages.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=167567914

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Created by MOE: https://github.com/google/moe
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The FakeClock allows to simulate timing behaviour including sleep time
for test cases.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=162345258

1. Move entire library from v2/library/ to v2/library/core
2. Add v2/library/all that depends on v2/library/core

Issue: #2139

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=150455693

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131393395

- The package is renamed to avoid conflicts with v1, should any
app wish to include both v1 and v2 for a period of time. This is
similar to the approach used by some other open source projects
(e.g. okhttp).
- Copyright year is updated everywhere for completeness.
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Created by MOE: https://github.com/google/moe
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