Use precomputed tables

[sethdusek]

Use pre-computed multiplication tables for generator where possible (secret key -> pk, generating public image of nonce in signing/verification, etc). Also pre-compute DlogProverInput.public_image() to avoid repeated EC operations in signing (helps performance when there are many secrets in Wallet).

Some benchmarks (Wallet with 1000 secrets, signing N inputs):

• cachedpk is with only eagerly-evaluated public image (a410eaf)
• precomputed+cachedpk uses generator table optimization + cachedpk
• Final is the result of all optimizations, along with some other smaller optimizations
  

Some small improvements to verification as well, tested on dbd86fdce57f3a5124e88ec1ee4b7289e450e059e21a74c303bf13bf0b924945, time to verify is down from 0.2s to 0.17s

[coveralls]

Pull Request Test Coverage Report for Build 16405540612

Details

• 62 of 69 (89.86%) changed or added relevant lines in 16 files are covered.
• 10 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.01%) to 78.438%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ergo-lib/src/chain/transaction/unsigned.rs	0	1	0.0%
ergotree-interpreter/src/eval/create_provedlog.rs	0	1	0.0%
ergotree-interpreter/src/sigma_protocol/private_input.rs	14	15	93.33%
ergo-lib/src/wallet/ext_secret_key.rs	9	13	69.23%

Files with Coverage Reduction	New Missed Lines	%
ergo-p2p/src/peer_info.rs	1	68.42%
ergotree-interpreter/src/sigma_protocol/private_input.rs	1	90.32%
ergotree-ir/src/mir/constant.rs	1	63.98%
ergotree-ir/src/mir/expr.rs	1	69.02%
ergo-p2p/src/peer_spec.rs	6	78.13%

Totals
Change from base Build 15758737784:	-0.01%
Covered Lines:	11961
Relevant Lines:	15249

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💛 - Coveralls