Jstz core: Introduce BinEncodable trait for consistent serialization

[ryutamago]

Context

The original Value design had the following issues:

• The Value trait required types to implement encode()
• But deserialization happened through standalone deserialize() function
• This meant a type could implement Value::encode() using one serialization format
  while the standalone deserialize() used a different format
• This could lead to silent failures where encoded data cannot be properly decoded

This PR ensures consistent serialization format through BinEncodable trait, removing potential for format mismatches. Additionally, it simplifies the storage/transaction APIs as the Value trait is bounded by the BinEncodable trait

related comment:
#767 (comment)

Task

Description

This PR introduces a dedicated BinEncodable trait to handle serialization consistently:

1. Creates a new BinEncodable trait with both encode/decode methods
2. Makes Value trait use BinEncodable as a bound
3. Provides automatic BinEncodable implementation for types with bincode's Encode + Decode traits
4. Removes standalone serialize/deserialize functions as well as the default encode config
5. Simplified the storage and transaction apis
6. Add docs to Value trait

Manually testing the PR

Unit tests for encoding:

cargo test --package jstz_core --lib -- encoding::tests --show-output

Deployed and ran sf manually.

[codecov]

Codecov Report

Attention: Patch coverage is 68.75000% with 30 lines in your changes missing coverage. Please review.

Project coverage is 48.49%. Comparing base (635c6ba) to head (53b96fc).

Files with missing lines	Patch %	Lines
crates/jstz_core/src/kv/transaction.rs	61.90%	7 Missing and 1 partial ⚠️
crates/jstz_node/src/services/accounts.rs	0.00%	8 Missing ⚠️
crates/jstz_core/src/bin_encodable.rs	83.33%	4 Missing and 2 partials ⚠️
crates/jstz_node/src/services/operations.rs	0.00%	4 Missing ⚠️
crates/jstz_core/src/kv/mod.rs	75.00%	0 Missing and 2 partials ⚠️
crates/jstz_core/src/kv/outbox.rs	0.00%	0 Missing and 1 partial ⚠️
crates/jstz_kernel/src/inbox.rs	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
crates/jstz_core/src/kv/value.rs	57.14% <ø> (+2.59%)	⬆️
crates/jstz_crypto/src/public_key_hash.rs	79.19% <100.00%> (ø)
crates/jstz_kernel/src/lib.rs	88.23% <100.00%> (ø)
crates/jstz_mock/src/host.rs	97.43% <100.00%> (+0.37%)	⬆️
crates/jstz_proto/src/executor/fa_deposit.rs	94.72% <ø> (ø)
crates/jstz_proto/src/executor/fa_withdraw.rs	94.57% <ø> (ø)
crates/jstz_proto/src/executor/smart_function.rs	85.81% <100.00%> (ø)
crates/jstz_proto/src/operation.rs	60.00% <100.00%> (-2.88%)	⬇️
crates/jstz_core/src/kv/outbox.rs	90.23% <0.00%> (ø)
crates/jstz_kernel/src/inbox.rs	74.32% <0.00%> (+0.45%)	⬆️
... and 5 more

... and 3 files with indirect coverage changes

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[ryutamago]

closing this as it's cherry picked into #767