[sanitizer] Support v2 and v3 capabilities

capget() and capset() may read or write more than one cap_user_data_t,
depending on the version field of cap_user_header_t. Currently the
code assumes it's just one, so MSan complains if an application uses
version 2 or 3, where two cap_user_data_ts are used.

Parse the header in order to determine the number of cap_user_data_ts.
Also add a test.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D143660