EVM: Fix Precompile Failure Modes & Implement Remaining Precompile Tests (filecoin-project#654)

* bn pair tests and errors

* add ec_recover test, fix broken implementation

* add modexp test, add more test cases for ec_recover

* only check lower bound for ec_recover

* Fix broken failure modes in precompiles
- ec_recover
- modexp
- ec_add
- ec_mul

Change error enum to include field error types + conversions
- forked bn to derive Eq on bn Errors

Add helper for reading padded bytes from input.

* rustfmt & clippy

* Update precompiles.rs

* use cow instead of custom container

* remove fork of bn

* remove bn for dep

* allocate ahead of time when reading sets of

* lazy_static secp256k1 lower bound

* left pad ecrecover

* hex literal and cargo lock

* add padding test

* space

* dont panic on modexp len

* few remaining nits

* rustfmt

* better read logic of bigints for modexp

* add notes to reading bigint lengths & refactor read group for more clarity

* rustfmt

Author: mriise

Cargo.lock

@@ -38,12 +38,13 @@ fixed-hash = { version = "0.7.0", default-features = false }
 impl-serde = { version = "0.3.2", default-features = false }
 arrayvec = { version = "0.7.2", features = ["serde"] }
 hex = "0.4.3"
+hex-literal = "0.3.4"
 substrate-bn = { version = "0.6.0", default-features = false }
 near-blake2 = { version = "0.9.1", git = "https://github.com/filecoin-project/near-blake2.git" }
+lazy_static = "1.4.0"
 
 [dev-dependencies]
 fil_actors_runtime = { path = "../../runtime", features = ["test_utils", "sector-default"] }
-hex-literal = "0.3.4"
 etk-asm = "^0.2.1"
 
 [features]