codegen: RuntimeClientPlugin not having access to a SymbolProvider

[syall]

RuntimeClientPlugin is used for a variety of codegen points, e.g. middleware registration:

smithy-go/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/integration/RuntimeClientPlugin.java

Line 138 in 7be1336

public Optional<MiddlewareRegistrar> registerMiddleware() {

However, middleware registration typically needs access to a symbol provider to correctly get the name of functions and such.

There should be a way to expose the symbol provider in RuntimeClientPlugin.

[lucix-aws]

getClientPlugins should also probably thread through the model and service shape / id much like the other integration APIs do (#467 (comment)).