winch: Introduce winch-environ (#6017)

This commit introduces the `winch-environ` crate. This crate's responsibility is
to provide a shared implementatation of the `winch_codegen::FuncEnv` trait,
which is Winch's function compilation environment, used to resolve module and
runtime specific information needed by the code generation, such as resolving
all the details about a callee in a WebAssembly module, or resolving specific
information from the `VMContext`.

As of this change, the implementation only includes the necessary pieces to
resolve a function callee in a WebAssembly module. The idea is to evolve the
`winch_codegen::FuncEnv` trait as we evolve Winch's code generation.

winch/filetests/Cargo.toml

@@ -12,6 +12,7 @@ edition.workspace = true
 winch-test-macros = {workspace = true}
 target-lexicon = { workspace = true }
 winch-codegen = { workspace = true, features = ['all-arch'] }
+winch-environ = { workspace = true }
 wasmtime-environ = { workspace = true }
 anyhow = { workspace = true }
 wat = { workspace = true }