[9.20] chg: nil: Suppress FreeBSD-specific TSAN false-positive lock-order-inversion

TSAN reports a lock-order-inversion (potential deadlock) issue in
`add_trace_entry()`.

While it is true that in one case a lock in the `isc_mem_t` structure is
locked first, and then a lock in the `FILE` structure is locked second,
and in the the second case it is the other way around, this isn't an
issue, because those are `FILE` structures for totally different files,
used in different parts of the code.

Closes #5266

Backport of MR !10355

Merge branch 'backport-5266-freebsd-suppress-tsan-lock-order-inversion-false-positive-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!10362