* Switch lightbeam from `wabt` to `wast`
Switch from a C++-based `*.wat` parser to a Rust-based parser
* Remove unneeded `wabt` dev-dependency from wasmtime-api
* Rewrite `wasmtime-wast` crate with `wast-parser`
This commit moves the `wasmtime-wast` crate off the `wabt` crate on to
the `wast-parser` crate which is a Rust implementation of a `*.wast` and
`*.wat` parser. The intention here is to continue to reduce the amount
of C++ required to build wasmtime!
* Use new `wat` and `wast` crate names
This adds a `--always-lightbeam` option as well as an `--always-cranelift`
option, to allow the compilation strategy to be selected via the
command-line. This also enables regular testing for Lightbeam.
* Transform DWARF sections into native format for wasm2obj and wasmtime.
Generate DWARF sections based on WASM DWARF.
Ignore some of debug_info/debug_line for dead code.
* Fix test
