[LUT HAL] Interface update

- Rename Lut.aidl to Luts.aidl. In Luts.aidl structure, we provides one
  array of offsets and one array of lutProperties. `offsets` is to store
  starting point of each lut memory region of the lut buffer. That is to
  say, multiple Luts are packed into one same ashmem region, and we use
  `offsets` to know each lut buffer's position.
- change the data type of `size` to int.
- doc update: use `ashmem_create_region` instead.

Bug: 329472100
Test: builds
Change-Id: Iea38afa722a28c55f2147c67e2222fcd8323d0d7