embed jsonrpc types from jsonrpc-core crate (#2801)

We should not depend on jsonrpc-core anymore:

* The project just announced it's no longer actively maintained[^1],
  preferring their new implementation in `jsonrpsee`.
* The types are too strict: we would benefit from removing some
  `#[serde(deny_unknown_fields)]` annotations to allow language
  servers that disrespect the spec[^2].
* We don't use much of the project. Just the types out of core.
  These are easy to embed directly into the `helix-lsp` crate.

[^1]: paritytech/jsonrpc#674
[^2]: #2786

helix-lsp/Cargo.toml

@@ -17,7 +17,6 @@ helix-core = { version = "0.6", path = "../helix-core" }
 anyhow = "1.0"
 futures-executor = "0.3"
 futures-util = { version = "0.3", features = ["std", "async-await"], default-features = false }
-jsonrpc-core = { version = "18.0", default-features = false } # don't pull in all of futures
 log = "0.4"
 lsp-types = { version = "0.93", features = ["proposed"] }
 serde = { version = "1.0", features = ["derive"] }

helix-lsp/src/client.rs

@@ -1,11 +1,11 @@
 use crate::{
+    jsonrpc,
     transport::{Payload, Transport},
     Call, Error, OffsetEncoding, Result,
 };
 
 use anyhow::anyhow;
 use helix_core::{find_root, ChangeSet, Rope};
-use jsonrpc_core as jsonrpc;
 use lsp_types as lsp;
 use serde::Deserialize;
 use serde_json::Value;