fix(json-rpc): exclude transaction-not-found errors from error policy

[filipdulic]

Description of change

• Return a dedicated JSON-RPC error code when a transaction is not found.
• Exclude this response from the full node error policy.
• Ensure zero-weight tallies are never sampled.
• Preserve the JSON-RPC client-error classification in the local Rust SDK.
• Continue counting the request toward the spam policy.
• Keep invalid requests and terminal transaction errors fully weighted.

Links to any relevant issues

Fixes #12522.

How the change has been tested

• Basic tests (linting, compilation, formatting, unit/integration tests)
• Patch-specific tests (correctness, functionality coverage)
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes

Release Notes

• Protocol:
• Nodes (Validators and Full nodes): Full nodes no longer count transaction-not-found responses toward the error policy. Zero-weight tallies are never sampled.
• Indexer:
• JSON-RPC: iota_getTransactionBlock now returns error code -32003 when a transaction is not found.
• GraphQL:
• CLI:
• Rust SDK: JSON-RPC errors expose and identify the transaction-not-found error code.
• gRPC:

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[muXxer]

Shouldn't this also exist for the get_object endpoint? If nodes pruned an object, the client also can't know that in advance, and this should not count as an error in the spam tally, but just as spam.

[filipdulic]

Shouldn't this also exist for the get_object endpoint? If nodes pruned an object, the client also can't know that in advance, and this should not count as an error in the spam tally, but just as spam.

dont we already handle this, a missing or pruned object returns NotExists and is a successfull IotaObjectResponse,