Fix: serde on enums

[zcabter]

Context

This PR fixes the awkward external tagging that serde uses for Json serialisation with the following changes:

1. Cryptos enums are marked with #[serde(untagged)]
2. Non-cryptos enums are marked as #[serde(tag = "_type")]

These changes ensures that we get generated code that makes sense in Typescript from #644

Manually testing the PR

Code should build, tests should pass
make

[codecov]

Codecov Report

Attention: Patch coverage is 89.65517% with 24 lines in your changes missing coverage. Please review.

Project coverage is 45.21%. Comparing base (7bed1ce) to head (716333c).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/jstz_node/src/api_doc.rs	93.33%	11 Missing ⚠️
crates/jstz_cli/src/run.rs	0.00%	4 Missing ⚠️
crates/jstz_cli/src/deploy.rs	0.00%	3 Missing ⚠️
crates/jstz_proto/src/receipt.rs	72.72%	1 Missing and 2 partials ⚠️
crates/jstz_crypto/src/public_key_hash.rs	0.00%	2 Missing ⚠️
crates/jstz_node/src/lib.rs	80.00%	0 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
crates/jstz_crypto/src/hash.rs	41.32% <100.00%> (+0.19%)	⬆️
crates/jstz_crypto/src/public_key.rs	44.79% <ø> (+1.04%)	⬆️
crates/jstz_crypto/src/secret_key.rs	32.25% <100.00%> (-1.43%)	⬇️
crates/jstz_crypto/src/signature.rs	43.97% <ø> (+0.40%)	⬆️
crates/jstz_proto/src/api/smart_function.rs	79.24% <100.00%> (ø)
crates/jstz_proto/src/context/account.rs	65.48% <100.00%> (ø)
crates/jstz_proto/src/executor/deposit.rs	100.00% <100.00%> (ø)
crates/jstz_proto/src/executor/fa_deposit.rs	95.35% <100.00%> (+0.04%)	⬆️
crates/jstz_proto/src/executor/fa_withdraw.rs	94.57% <ø> (ø)
crates/jstz_proto/src/executor/smart_function.rs	85.71% <100.00%> (-0.05%)	⬇️
... and 7 more

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7bed1ce...716333c. Read the comment docs.