This commit changes the APIs in the `wasmtime` crate for configuring the
pooling allocator. I plan on adding a few more configuration options in
the near future and the current structure was feeling unwieldy for
adding these new abstractions.
The previous `struct`-based API has been replaced with a builder-style
API in a similar shape as to `Config`. This is done to help make it
easier to add more configuration options in the future through adding
more methods as opposed to adding more field which could break prior
initializations.
Previously, much of the logic for generating the various objects needed
for fuzzing was concentrated primarily in `generators.rs`. In trying to
piece together what code does what, the size of the file and the light
documentation make it hard to discern what each part does. Since several
generator structures had been split out as separate modules in the
`generators/` directory, this change takes that refactoring further by
moving the structures in `generators.rs` to their own modules. No logic
changes were made, only the addition of documentation in a few places.
