fix: use Bitgesell RPC JSON crate name

[manuelsampedro1]

This fixes a workspace build break in the Rust Bitgesell RPC client fork.

The client crate still depended on bitcoincore-rpc-json, but the local JSON crate in this repository is named bitgesellcore-rpc-json. A clean cargo test --workspace --lib therefore failed before compilation with:

error: no matching package named `bitcoincore-rpc-json` found
location searched: ../json

Changes:

• point the client dependency at bitgesellcore-rpc-json
• update public re-export/import names to bitgesellcore_rpc_json
• update the integration test and examples to use bitgesellcore_rpc

Validation:

• cargo test --workspace --lib
• cargo test --workspace
• cargo test --workspace --examples

Bounty context: BitgesellOfficial/bitgesell#39

[MyTH-zyxeon]

Review assist for maintainers:

This looks like a focused crate-name alignment from the upstream bitcoincore-rpc* names to the Bitgesell crate names in the client/examples/integration-test surfaces. I checked the patch scope: dependency package rename in client/Cargo.toml, public JSON re-export rename in client/src/lib.rs, examples updated to bitgesellcore_rpc, integration-test imports updated, and the log target/auth type references follow the same rename.

Suggested merge checks:

• Run cargo check --workspace or the repo's equivalent matrix to confirm bitgesellcore-rpc-json resolves locally from ../json and the public json re-export still compiles.
• Search for remaining bitcoincore_rpc / bitcoincore-rpc-json references in client/examples, client/src, and integration_test so the rename does not leave mixed crate names in buildable code.
• Compile the two examples and the integration-test crate without requiring live RPC credentials, then keep any node-backed RPC smoke test as a maintainer-only follow-up.

I do not see a wallet/key or live-node behavior change in this patch as written; the main acceptance criterion is that the crate rename is complete and buildable without stale upstream crate identifiers.