Reuse wasmtime instances, the PR (#5567)

* Preserve a single wasmtime instance.

* Sketch of wasm instance reusing.

* Refactor and docs.

* Rename state_snapshot to util module.

* Renaming.

* Comments.

* Error handling

* More fixes.

substrate/Cargo.lock

@@ -6250,6 +6250,7 @@ dependencies = [
  "derive_more",
  "log",
  "parity-scale-codec",
+ "parity-wasm 0.41.0",
  "sp-allocator",
  "sp-core",
  "sp-runtime-interface",
@@ -6264,7 +6265,6 @@ version = "0.8.0-alpha.5"
 dependencies = [
  "log",
  "parity-scale-codec",
- "parity-wasm 0.41.0",
  "sc-executor-common",
  "sp-allocator",
  "sp-core",
@@ -6278,6 +6278,8 @@ name = "sc-executor-wasmtime"
 version = "0.8.0-alpha.5"
 dependencies = [
  "assert_matches",
+ "cranelift-codegen",
+ "cranelift-wasm",
  "log",
  "parity-scale-codec",
  "parity-wasm 0.41.0",
@@ -6288,6 +6290,8 @@ dependencies = [
  "sp-runtime-interface",
  "sp-wasm-interface",
  "substrate-wasmtime",
+ "substrate-wasmtime-runtime",
+ "wasmtime-environ",
 ]
 
 [[package]]