Make the TSan report capture data structure anonymous.

This was using `struct data` which is way to common a name to use in
an lldb expression, and was causing occasional failures in the
TSan report gatherer.  The structure doesn't need to have a tag,
so remove it to avoid future problems.

The same job was done for the other sanitizers in D145569, but this
one was overlooked.

Differential Revision: https://reviews.llvm.org/D149394