Workaround compiler crashes seen by some toolchains (#110)

Motivation:

The toolchains installed via swiftly seem to trip over some compilation
issues related to lifetimes in release builds. This has been reported
upstream but for now we should workaround this to unblock users
installing toolchains with Swiftly.

Modifications:

- Remove the `~Copyable`s from the `WrappedChannel` state machine

Result:

- Compiles in release mode with Swiftly installed toolchains

Sources/GRPCNIOTransportCore/Client/WrappedChannel/WrappedChannel+State.swift

@@ -19,7 +19,7 @@ internal import NIOHTTP2
 
 @available(gRPCSwiftNIOTransport 1.2, *)
 extension HTTP2ClientTransport.WrappedChannel {
-  enum State: ~Copyable {
+  enum State {
     case idle(Idle)
     case configuring(Configuring)
     case configured(Configured)
@@ -27,7 +27,7 @@ extension HTTP2ClientTransport.WrappedChannel {
     case shuttingDown
     case shutDown
 
-    struct Idle: ~Copyable {
+    struct Idle {
       var queue: RequestQueue<NIOHTTP2Handler.AsyncStreamMultiplexer<Void>>
 
       init() {
@@ -35,7 +35,7 @@ extension HTTP2ClientTransport.WrappedChannel {
       }
     }
 
-    struct Configuring: ~Copyable {
+    struct Configuring {
       var queue: RequestQueue<NIOHTTP2Handler.AsyncStreamMultiplexer<Void>>
 
       init(from state: consuming Idle) {
@@ -43,7 +43,7 @@ extension HTTP2ClientTransport.WrappedChannel {
       }
     }
 
-    struct Configured: ~Copyable {
+    struct Configured {
       var queue: RequestQueue<NIOHTTP2Handler.AsyncStreamMultiplexer<Void>>
       var multiplexer: NIOHTTP2Handler.AsyncStreamMultiplexer<Void>
 
@@ -56,7 +56,7 @@ extension HTTP2ClientTransport.WrappedChannel {
       }
     }
 
-    struct Ready: ~Copyable {
+    struct Ready {
       var multiplexer: NIOHTTP2Handler.AsyncStreamMultiplexer<Void>
 
       init(from state: consuming Configured) {