TrustThresholdFraction: allow to be initialized with value 1

[plafer]

Closes: #1208

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Added entry in .changelog/

[mzabaluev]

Agree, we should follow what the Go implementation does here.

Fix the docs and it should be good to go.
The rustdoc problem should have been fixed in #1212, so merge/rebase to get rid of it.

[mzabaluev]

This doc needs to be updated too, then?

[plafer]

7c4888a

[codecov-commenter]

Codecov Report

Merging #1209 (7c4888a) into main (035acab) will decrease coverage by 0.0%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #1209     +/-   ##
=======================================
- Coverage   64.0%   63.9%   -0.1%     
=======================================
  Files        253     253             
  Lines      21636   21636             
=======================================
- Hits       13851   13839     -12     
- Misses      7785    7797     +12     

Impacted Files	Coverage Δ
tendermint/src/trust_threshold.rs	92.9% <100.0%> (ø)
config/src/config.rs	54.7% <0.0%> (-1.3%)	⬇️
testgen/src/header.rs	82.9% <0.0%> (-1.2%)	⬇️
testgen/src/vote.rs	84.0% <0.0%> (-0.9%)	⬇️
light-client-verifier/src/types.rs	38.1% <0.0%> (-0.6%)	⬇️
abci/src/server.rs	9.2% <0.0%> (-0.2%)	⬇️
tendermint/src/node.rs	64.1% <0.0%> (+0.1%)	⬆️

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