gh-116088: Insert bottom checks after all sym_set_...() calls (#116089)

gh-116088: Insert bottom checks after all sym_set_...() calls (#116089)

This changes the `sym_set_...()` functions to return a `bool` which is `false`
when the symbol is `bottom` after the operation.

All calls to such functions now check this result and go to `hit_bottom`,
a special error label that prints a different message and then reports
that it wasn't able to optimize the trace. No executor will be produced
in this case.