PE disassembly can panic

[ranweiler]

The PE disassembly uses a FixedBitSet to flag coverage feature sites. However, the FixedBitSet::insert() method panics if the bit index is out of bounds.

At a minimum, replace uses of insert() with a non-panicking usage. This doesn't appear to exist, so we could use something like a private extension trait that adds a method like try_insert(&mut self, bit: usize) -> Result<()>.

AB#43103025