Remove borsh schemas and the encoding spec

[sug0]

Describe your changes

Borsh schemas were only depended upon by the namada_encoding_spec crate. Therefore, we can remove schemas, which were an unstable feature in borsh, anyway.

Indicate on which release or other PRs this topic is based on

v0.31.5

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[sug0]

might need to rebuild wasms for tests

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (c733be2) 53.38% compared to head (39b54dc) 53.76%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
crates/tx/src/types.rs	72.72%	3 Missing ⚠️
.../protocol/transactions/ethereum_events/eth_msgs.rs	0.00%	1 Missing ⚠️
crates/proof_of_stake/src/types/mod.rs	75.00%	1 Missing ⚠️
crates/sdk/src/queries/vp/pos.rs	0.00%	1 Missing ⚠️
crates/vote_ext/src/lib.rs	50.00%	1 Missing ⚠️
crates/vote_ext/src/validator_set_update.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2682      +/-   ##
==========================================
+ Coverage   53.38%   53.76%   +0.38%     
==========================================
  Files         302      301       -1     
  Lines      103403   102602     -801     
==========================================
- Hits        55198    55162      -36     
+ Misses      48205    47440     -765     

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[murisi]

Would keeping the BorshSchema's in Namada be harmful? I ask because these schemas would be extremely useful in describing our serialized formats to external collaborators like Zondax. Providing them with the (automatically derived) schemas would reduce the time we spend manually specifying serializations and simultaneously ease collaborators' process of writing and auditing parsers for our transactions in languages like C. The other more niche use case for these schemas is to automate the construction of parsers like in: #2732 .

[sug0]

we'll be keeping borsh schemas in Namada, as they might be handy in the future