Enable userspace snapshots for OTA

Bug: 202784018

Test: Full/Incremental OTA tested on CF, Pixel

OTA Merge time performance on Pixel (bramble)

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Incremental - OTA - 389M

OTA Operations:

system - Copy-ops: 34060 Zero-ops: 678 Replace-ops: 93846 Xor-ops: 75490

product - Copy-ops: 241742 Zero-ops: 1970 Replace-ops: 292890 Xor-ops: 80763

vendor - Copy-ops: 110285 Zero-ops: 660 Replace-ops: 62163 Xor-ops: 23474

system_ext_b - Copy-ops: 44509 Zero-ops: 426 Replace-ops: 39475 Xor-ops: 44628

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1: VAB - Compression with dm-snapshot (on Android S)

Merge-time = 344 seconds (~5.7 minutes)

2: VAB - Compression with user-snapshot (on Android T)

Merge-time = 53 seconds

3: VAB - Without compression (using kernel COW format)

Merge-time = 33 seconds

Compared to Android S, merge time improves by 84% with user-snapshots on Android T.

The 20 seconds difference between (2) and (3) is because of two phase merge during compression which essentially serializes merge start time between partitions.

On (3), there is no two phase merge as all the partition starts merge at the same time.

When there is no two phase merge involved, (2) and (3) are nearly identical.

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Full OTA - 1.8G

1: VAB - Compression with dm-snapshot (on Android S)

Merge-time = 40 seconds

2: VAB - Compression with user-snapshot (on Android T)

Merge-time = 32 seconds

3: VAB - Without compression (using kernel COW format)

Merge-time = 32 seconds

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Presubmit OTA testing enabled on Cuttlefish for ~1 Week with
the feature enabled.

https://v2-dot-atp.googleplex.com/tests/asit/ota/incremental_mixed_resume



Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: I88d15b94a48799996f38755063319269a3d70723