Use runtime_host instead of read_only_runtime_host in JSON-RPC code

[tomaka]

Fix #254

In practice, this affects not only state_call but also state_getMetadata, system_accountNextIndex, and payment_queryInfo. Of course, the last three aren't really affected since the runtime function being called is hardcoded.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       +6512 ┊ smoldot_light::json_rpc_service::Background<TPlat>::runtime_lock::{{closure}}::h11893006d1b4d89a
       -6512 ┊ smoldot_light::json_rpc_service::Background<TPlat>::runtime_lock::{{closure}}::ha437a247f4ae2730
        +726 ┊ smoldot::executor::runtime_host::run::h6353e83230970145
        +696 ┊ smoldot::executor::runtime_host::run::hd0a03319c3bbe6ef
        +655 ┊ smoldot::executor::runtime_host::run::h5bfea10e92832737
        +649 ┊ smoldot::executor::runtime_host::run::had92c81c80d1fbfb
        -395 ┊ smoldot::executor::read_only_runtime_host::run::h422c5e8a0c47f40b
        -368 ┊ smoldot::executor::read_only_runtime_host::run::hac4040d1e839570b
        -327 ┊ smoldot::executor::read_only_runtime_host::run::hd35ee40c4fe7f380
        +302 ┊ <smoldot_light::json_rpc_service::RuntimeCallError as core::fmt::Display>::fmt::h6b5966d41951910f
        -278 ┊ <smoldot_light::json_rpc_service::RuntimeCallError as core::fmt::Display>::fmt::h41d04796709a343d
        -250 ┊ core::ptr::drop_in_place<smoldot_light::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>::runtime_lock::{{closure}}>::h0103481ef2c37f65
        +250 ┊ core::ptr::drop_in_place<smoldot_light::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>::runtime_lock::{{closure}}>::h4c508df58b0e942b
        -243 ┊ <smoldot::executor::read_only_runtime_host::ErrorDetail as core::fmt::Display>::fmt::h96b8f3f7d561c883
        +231 ┊ <&T as core::fmt::Display>::fmt::hd862f2cf1bc458c7
        +180 ┊ smoldot_light::json_rpc_service::Background<TPlat>::handle_request::{{closure}}::h9a0dc66fb4c1420c
        -122 ┊ core::ptr::drop_in_place<smoldot_light::json_rpc_service::state_chain::<impl smoldot_light::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::state_call::{{closure}}>::h854de0bf08144451
        +122 ┊ core::ptr::drop_in_place<smoldot_light::json_rpc_service::state_chain::<impl smoldot_light::json_rpc_service::Background<smoldot_light_wasm::platform::Platform>>::state_call::{{closure}}>::heea44efbf8a5750f
        -116 ┊ <T as alloc::string::ToString>::to_string::h0de603db597f7204
        +116 ┊ <T as alloc::string::ToString>::to_string::h494fd2e92dee66ef
        +112 ┊ ... and 32 more.
       +2048 ┊ Σ [52 Total Rows]