Improve remote-externalities (#8397)

* make builder generic to allow using different hash types

* expose "cache", "block_number" and "modules" as cli options for live state

* Change Builder to be generic over Block instead of Hash
add rpc method to get hash from block number
allow passing of block numbers and hashes

* fix live tests

* fix formatting in utils/frame/remote-externalities/src/lib.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* change cli to only accept block hashes
break up lines that were too long
use starts_with instead of match s.get
use unwrap_or_default instead of unwrap_or(Vec::new())

* improve error message

* fix indentation

* replace Block with sp_runtime::testing::Block

* Move cache test out of remote-test feature tests
Add cache file (contains only "Proxy" module) for local test

* simplify match expression to and_then

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Combine the two cfg attributes into one

Co-authored-by: David <dvdplm@gmail.com>

* Restrict visibility of test_prelude use statements to crate level

* Fix usage of and_then

* Rename cache to snapshot

* Remove fully qualified path for Debug

* Refine naming. snapshot to state_snapshot

* Remove unnecessary comment

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: David <dvdplm@gmail.com>

substrate/utils/frame/remote-externalities/Cargo.toml

@@ -25,9 +25,10 @@ codec = { package = "parity-scale-codec", version = "2.0.0" }
 
 sp-io = { version = "3.0.0", path = "../../../primitives/io" }
 sp-core = { version = "3.0.0", path = "../../../primitives/core" }
+sp-runtime = { version = "3.0.0", path = "../../../primitives/runtime" }
 
 [dev-dependencies]
-async-std = { version = "1.6.5", features = ["attributes"] }
+tokio = { version = "0.2", features = ["macros"] }
 
 [features]
 remote-test = []