Split out verifier parts of tendermint-light-client to tendermint-light-client-verifier (Backported to v0.23)

[soareschen]

This is a copy of #1071 that targets the v0.23.x branch. Due to the conflicts caused by moved files, the patch has the be applied in a rather convoluted way:

In the first copy of tendermint-rs src:

1. git checkout soares/light-client-verifier
2. git checkout -b soares/light-client-verifier-v0.23
3. git reset v0.23.x
4. git add light-client*
5. git add tools/kvstore-test
6. git commit
7. git clean -fd

In the second copy of tendermint-rs src:

1. git checkout v0.23.x
2. git reset master
3. Note the unstaged changes in light-client and light-client-js.
   3.1. I'm not sure if git diff would automatically do any smart diff based on a merge base. So doing git reset is a more guaranteed way to see the real diffs.

Finally:

1. Apply the unstaged changes in the second copy manually to the first copy of tendermint-rs.
   1.1. This cannot be automated due to moved files
2. git commit on first copy.

Due to the complicated steps to construct this PR. I'd hope that #1071 and this PR can be merged with minimal further changes. Otherwise for every change made I'd have to carefully cherry-pick the new commits and hope that there are no conflict raised.

• 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/

[codecov-commenter]

Codecov Report

Merging #1072 (808fd46) into v0.23.x (578289e) will increase coverage by 1.6%.
The diff coverage is 78.5%.

@@            Coverage Diff            @@
##           v0.23.x   #1072     +/-   ##
=========================================
+ Coverage     65.7%   67.3%   +1.6%     
=========================================
  Files          210     212      +2     
  Lines        20658   20171    -487     
=========================================
+ Hits         13575   13593     +18     
+ Misses        7083    6578    -505     

Impacted Files	Coverage Δ
light-client-js/src/lib.rs	3.7% <ø> (ø)
light-client-js/tests/web.rs	100.0% <ø> (ø)
light-client-verifier/src/errors.rs	3.7% <ø> (ø)
...client-verifier/src/operations/commit_validator.rs	98.0% <ø> (ø)
light-client-verifier/src/operations/hasher.rs	100.0% <ø> (ø)
...ght-client-verifier/src/operations/voting_power.rs	98.0% <ø> (ø)
light-client-verifier/src/options.rs	0.0% <0.0%> (ø)
light-client-verifier/src/predicates.rs	97.4% <ø> (ø)
light-client-verifier/src/verifier.rs	87.9% <ø> (ø)
light-client/examples/light_client.rs	0.0% <0.0%> (ø)
... and 34 more

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