Fix flakiness of sensor VTS test cases

* Correction of testBatchingOperation wait logic.
* Enlarge buffer size for direct report testing.

Original cl links: ag/3053316 and ag/2759224

Bug: 64732324
Bug: 63529148
Bug: 67439052
Test: testBatchingOperation passes consistently
Test: direct report tests pass on 2016 pixel device

Merged-In: Id4e8075e249f3658f5683d53d6dc8403ee32bc4a
Merged-In: Ibe1d076c24dc2cfe61dfd19aa5055c9075aa9e14
Change-Id: Id4e8075e249f3658f5683d53d6dc8403ee32bc4a