fix(kt): enable gRPC server compression (#569)

Per gRPC docs referencing [this
code](https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/experimental/CompressingHelloWorldServerAllMethods.java).

```
🐚 ~/dev/ftl $ ftl call alice.echo
{"message":"Hello, null!"}
🐚 ~/dev/ftl $ ftl call bob.echo
{"message":"Hello, null! Hello, testing123!"}
```

Justfile

@@ -0,0 +1,8 @@
+install-jars: && install-generator-jar install-runtime-jar
+  mvn install
+
+install-generator-jar:
+  mvn -pl :ftl-generator install
+
+install-runtime-jar:
+  mvn -pl :ftl-runtime install

bin/.just-1.15.0.pkg

@@ -0,0 +1 @@
+hermit

bin/just

@@ -0,0 +1 @@
+.just-1.15.0.pkg

kotlin-runtime/ftl-runtime/src/main/kotlin/xyz/block/ftl/server/ServerInterceptor.kt

@@ -21,6 +21,8 @@ internal class ServerInterceptor : ServerInterceptor {
     headers: Metadata?,
     next: ServerCallHandler<ReqT, RespT>?
   ): ServerCall.Listener<ReqT> {
+    call?.setCompression("gzip")
+
     var context = Context.current()
 
     headers?.getAll(callersMetadata)?.apply {