Fixes #966, #797 and other clean ups

[afsalthaj]

Fixes #966, #797, and other cleanups:

• We already have a WorkerServiceRibInterpreter service in the worker-service module, which handles the details of the worker-gateway (worker-service). To maintain consistency, this PR introduces WorkerServiceRibCompiler, responsible for compiling Rib Expr in a way specific to the worker-gateway. Example: WorkerServiceRibCompiler ensures that the only allowed global variable in the Rib scrip is a request.

• Removed the pure_evaluate function in the worker-service module. It was slightly harder to reason about, as it primarily dealt with evaluating Rib expressions without function calls (e.g., resolving a worker-name expression). This has been replaced with directly calling the rib::interpret_pure function. This is useful anytime we need to evaluate a Rib expression anywhere in Golem.

• The function-type registry is a map of RegistryKey to RegistryValue. RegistryKey is a FunctionName, but it included includes Enum, Variant, etc. As I was improving Rib, I find this part confusing, so I cleaned it up. To begin with, I wanted to treat everything as a generic function call and delegate the responsibility of differenting whether it is a Variant/Enum or actual worker-function call to the Rib Interpreter. However, that turned out to be a long-term goal with many brittle logic points. So it is still almost the same except that RegistryValue will hold the information whether or not it is a Variant. This allows safer pattern match and logical decisions during type inference. This adjustment allows for more context-aware error messages. Example: Instead of "wrong number of arguments to register-user," we can have "wrong number of arguments to variant register-user". Likewise, we have the flexibility to add more information in the error messages.

• Renaming of some important variables, adding an fixing comments making it easier to understand the workflow of serving a custom http request for a new developer.

• Early error messages for invalid function calls before going to other phases of compilation which makes the error message more opaque due to extra details.

Unknown function call: `foo`

Unknown resource constructor call: `golem:it/api.{cart0(user_id).add-item}`. Resource `cart0` doesn't exist

Unknown resource method call golem:it/api.{cart(user_id).foo}. `foo` doesn't exist in resource `cart`

Incorrect number of arguments for function `foo`. Expected 1, but provided 2

Incorrect number of arguments for resource constructor `cart`. Expected 1, but provided 2

Invalid type for the argument in resource method `golem:it/api.{cart(user_id).add-item}`. 
Expected type `record`, but provided argument `\"foo\"` is a `str`

etc

[afsalthaj]

The error messages in the PR description is a candidate for review