Upgrade to Rust 1.87 (#7346)

I ignored some new clippy lints about large differences between enum variants.
We can always revisit these later (the compiler suggests boxing them so
that the enum variants are similar size)

rust/kcl-lib/src/engine/conn.rs

@@ -67,6 +67,7 @@ pub struct TcpRead {
 
 /// Occurs when client couldn't read from the WebSocket to the engine.
 // #[derive(Debug)]
+#[allow(clippy::large_enum_variant)]
 pub enum WebSocketReadError {
     /// Could not read a message due to WebSocket errors.
     Read(tokio_tungstenite::tungstenite::Error),