Crypto verify benchmarks

[maurolacy]

Implements digital signature verification benchmarks. Related to #758.

Some results on my machine:

$ cargo bench
    Finished bench [optimized] target(s) in 0.21s
     Running .../cosmwasm/target/release/deps/main-eaae5b3aaca9452a
Crypto/secp256k1_verify time:   [175.56 us 175.67 us 175.82 us]                                   
                        change: [-0.1863% -0.0758% +0.0316%] (p = 0.20 > 0.05)
                        No change in performance detected.
Crypto/secp256k1_recover_pubkey                                                                           
                        time:   [176.09 us 176.24 us 176.39 us]
                        change: [-0.0200% +0.0859% +0.2043%] (p = 0.16 > 0.05)
                        No change in performance detected.
Found 1 outliers among 12 measurements (8.33%)
  1 (8.33%) high mild
Crypto/ed25519_verify   time:   [70.576 us 70.609 us 70.648 us]                                  
                        change: [+0.0043% +0.1324% +0.2619%] (p = 0.06 > 0.05)
                        No change in performance detected.
Crypto/ed25519_batch_verify_five                                                                           
                        time:   [247.89 us 248.13 us 248.33 us]
                        change: [+0.0201% +0.1410% +0.2761%] (p = 0.04 < 0.05)
                        Change within noise threshold.

$  

ed25519_batch_verify_five verifies a batch of five entries (~50 us per entry; not bad). I'll now add some more benches for this, i. e. ed25519_batch_verify_one, two, three, ...

[webmaster128]

Nice. Could you add a block to the package readme how to execute (see vm's README)? Could you execute the benchmarks in the benchmarking CI job?

[webmaster128]

Nice. Just the update to Rust 1.49.0, then merge