Update to deprecations in ed25519 1.3

[mzabaluev]

Fixes: #1023

As of release 1.3.0, ed25519 deprecates the standalone SIGNATURE_LENGTH constant in favor of the Signature::BYTE_SIZE associated item. Also, the Signature::new constructor is deprecated in favor of Signature::from_bytes.
Update the code to not trigger the deprecation lints.

In turn, deprecate what was formerly the reexport of that constant in the tendermint API.

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests - pure refactoring, exercised by existing tests.
• Added entry in .changelog/

[codecov-commenter]

Codecov Report

Merging #1024 (63b3aab) into master (9690eca) will decrease coverage by 0.0%.
The diff coverage is 100.0%.

@@           Coverage Diff            @@
##           master   #1024     +/-   ##
========================================
- Coverage    66.1%   66.0%   -0.1%     
========================================
  Files         209     209             
  Lines       20764   20760      -4     
========================================
- Hits        13726   13719      -7     
- Misses       7038    7041      +3     

Impacted Files	Coverage Δ
tendermint/src/signature.rs	55.0% <ø> (+0.5%)	⬆️
tendermint/src/proposal.rs	90.4% <100.0%> (-0.3%)	⬇️
tendermint/src/test.rs	100.0% <100.0%> (ø)
tendermint/src/vote.rs	76.6% <100.0%> (+0.3%)	⬆️
tendermint/src/vote/sign_vote.rs	96.5% <100.0%> (ø)
testgen/src/vote.rs	84.0% <100.0%> (ø)
config/src/config.rs	55.2% <0.0%> (-1.3%)	⬇️
testgen/src/validator.rs	86.7% <0.0%> (-0.8%)	⬇️
tendermint/src/node.rs	63.5% <0.0%> (ø)
... and 1 more

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[romac]

Sweet, thanks @mzabaluev! Will leave it to @thanethomson to take another look and do the merge.

[mzabaluev]

To expand on this: it's probably not useful for non-test API users to have a Default impl for Vote, and there is potential for inadvertent misuse that is hard to audit for.

For test users, a dedicated helper fn would serve just as well, unless there are some commonly used cases that are more ergonomic with a Default impl. The dedicated function will be easy to find in code.

[romac]

Agreed, a dedicated helper fn sounds like the way to go. As far as I can tell this Default instance is only used in this one test (both directly via Vote::default() and indirectly via ..Default::default):

tendermint-rs/tendermint/src/vote/sign_vote.rs

Line 277 in 9690eca

fn test_sign_bytes_compatibility() {

[romac]

Tracked in #1025

[karim-agha]

Can you please merge this? It's blocking my build.