Re-add block_by_hash Tendermint endpoint

[fmorency]

Links #832.

Re-implements the block_by_hash RPC, which returns an optional block.

I applied the patch from #1089 and fixed the tendermint::Hash encoding/decoding to accommodate discrepancies in how the Tendermint RPC encodes this field for different RPC interfaces.

Relates to #942

CC @hansl

• 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 #1206 (018f1db) into main (00401ae) will decrease coverage by 0.0%.
The diff coverage is 43.0%.

@@           Coverage Diff           @@
##            main   #1206     +/-   ##
=======================================
- Coverage   64.0%   63.9%   -0.1%     
=======================================
  Files        250     253      +3     
  Lines      21554   21634     +80     
=======================================
+ Hits       13798   13836     +38     
- Misses      7756    7798     +42     

Impacted Files	Coverage Δ
rpc/src/abci/tag.rs	42.8% <ø> (ø)
rpc/src/client.rs	4.8% <0.0%> (-0.2%)	⬇️
rpc/src/client/bin/main.rs	0.3% <0.0%> (-0.1%)	⬇️
rpc/src/endpoint/tx.rs	25.0% <ø> (ø)
rpc/src/serializers/tx_hash_base64.rs	52.1% <ø> (ø)
tools/rpc-probe/src/common.rs	0.0% <0.0%> (ø)
rpc/src/endpoint/block_by_hash.rs	10.0% <10.0%> (ø)
rpc/src/method.rs	31.2% <50.0%> (+0.1%)	⬆️
rpc/src/serializers/tm_hash_base64.rs	52.1% <52.1%> (ø)
rpc/src/serializers/opt_tm_hash_base64.rs	57.1% <57.1%> (ø)
... and 7 more

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[thanethomson]

Thanks for this @fmorency!