light-client: Replace serde_cbor with serde_json

[devashishdxt]

Fixes #1026.
Fixes #1038.

• 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/

[xla]

Bice, just a small nit.

[xla]

٩(˘◡˘)۶

[codecov-commenter]

Codecov Report

Merging #1133 (088f320) into master (cd3e391) will not change coverage.
The diff coverage is 83.3%.

@@          Coverage Diff           @@
##           master   #1133   +/-   ##
======================================
  Coverage    64.7%   64.7%           
======================================
  Files         231     231           
  Lines       15637   15637           
======================================
  Hits        10121   10121           
  Misses       5516    5516           

Impacted Files	Coverage Δ
light-client/src/store/sled/utils.rs	72.0% <66.6%> (ø)
light-client/src/errors.rs	84.2% <100.0%> (ø)
testgen/src/vote.rs	84.8% <0.0%> (-0.9%)	⬇️
testgen/src/light_block.rs	76.6% <0.0%> (+0.5%)	⬆️

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[devashishdxt]

@xla This PR was merged but I don't see these changes in main branch.

[thanethomson]

main is effectively a fork off of tendermint-rs v0.23.x, since Tendermint Core v0.35/v0.36 were abandoned. See #1179

This would need to be ported across to main again.