Making caching support optional in Wasmtime (#2119)

This commit moves all of the caching support that currently lives in
`wasmtime-environ` into a `wasmtime-cache` crate and makes it optional. The
goal here is to slim down the `wasmtime-environ` crate and clearly separate
boundaries where caching is a standalone and optional feature, not intertwined
with other crates.

crates/environ/Cargo.toml

@@ -21,31 +21,11 @@ wasmparser = "0.59.0"
 lightbeam = { path = "../lightbeam", optional = true, version = "0.19.0" }
 indexmap = { version = "1.0.2", features = ["serde-1"] }
 thiserror = "1.0.4"
-directories = "2.0.1"
-sha2 = "0.8.0"
-base64 = "0.12.0"
 serde = { version = "1.0.94", features = ["derive"] }
-bincode = "1.1.4"
 log = { version = "0.4.8", default-features = false }
-zstd = "0.5"
-toml = "0.5.5"
-file-per-thread-logger = "0.1.1"
 more-asserts = "0.2.1"
 cfg-if = "0.1.9"
 gimli = "0.21"
 
-[target.'cfg(target_os = "windows")'.dependencies]
-winapi = "0.3.7"
-
-[target.'cfg(not(target_os = "windows"))'.dependencies]
-libc = "0.2.60"
-errno = "0.2.4"
-
-[dev-dependencies]
-tempfile = "3"
-pretty_env_logger = "0.4.0"
-filetime = "0.2.7"
-lazy_static = "1.3.0"
-
 [badges]
 maintenance = { status = "actively-developed" }