rpc: Update jsonrpsee v0.15.1 (#11939)

* Bump jsonrpsee to v0.15.1

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Update cargo.lock

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc-servers: Adjust RpcMiddleware to WS and HTTP traits

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/author: Use `SubscriptionSink`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/chain: Use `SubscriptionSink`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/state:  Use `SubscriptionSink`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/finality-grandpa: Use `SubscriptionSink`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/beefy: Use `SubscriptionSink`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* client: Extract RPC string result from queries

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Apply rust-fmt

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Fix warnings

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Fix testing

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/tests: Remove trailing comma

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc: Use `SubscriptionResult` for implementations

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc: Remove comment

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc: Delegate middleware calls to `RpcMiddleware`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc: Remove comment

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Revert Cargo.lock

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Update Cargo.lock with minimal changes

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc: Update imports for `SubscriptionResult`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Apply cargo fmt

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc/tests: Submit raw json requests to validate DenyUnsafe

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>