Add system_other partition props to Soong's misc_info.txt

Implementation Details
- Expand FilesystemInfo with some Avb* props. `system_other` will use
  this info exported by `system` to create system_other entries for
misc_info.txt. This is necessary since system_other does not contain
sufficient information to create a standalone buildPropFile, and reuses
the buildPropFile of system in `build_image` invocation
- Harcode rollback_index to the timestamp parsed from
  `PlatformSecurityPatch`. Most products (including cuttlefish) do not
use a product config variable to override the rollback_index.
Eventually, we should dynamically get this value from one of the vbmeta
partitions.

Bug: 398036609
Test: Built Make and Soong misc_info.txt
Test: No diff in system_other entries

Change-Id: Iadb0ee34d948cb15cd5a59b0dff7bf7fc64024ed