* YJIT: Fix `Struct` accessors not firing tracing events

Reading and writing to structs should fire `c_call` and `c_return`, but
YJIT wasn't correctly dropping those calls when tracing.
This has been missing since this functionality was added in 3081c831,
but the added test only fails when ran in isolation with
`--yjit-call-threshold=1`. The test sometimes failed on CI.

* RJIT: YJIT: Fix `Struct` readers not firing tracing events

Same issue as YJIT, but it looks like RJIT doesn't support writing to
structs, so only reading needs changing.