Command support in REPL

[afsalthaj]

Fix #1606

Commands in REPL. Implemented in a way golem-cli (or wasmtime) should be able to extend or override command set (as discussed during retreat)

There is an integration with Clap but note that golem_rib_repl's own Command trait do not enforcing users to use Clap for parsing input.

Adding new commands (and overriding)

pub struct TypeInfo;

impl Command for TypeInfo {
    type Input = Expr;
    type Output = AnalysedType;
    type InputParseError = RibCompilationError;
    type ExecutionError = RibCompilationError;
   
   // implement functions
}

let mut registry = CommandRegistry::default();

// push needs an instance of UntypedCommand, and every Command already has an instance of UntypedCommand
registry.push(MyCustomCommand); 

let repl = RibRepl::bootstrap(RibReplConfig { registry });

repl.run()

Overriding built-in commands from golem-cli (if needed)

• There is already CommandRegistry::built_in(). type-info is part of built_in.

• These commands can be overriden by golem-cli (or wasmtime) if needed. Example: if golem-cli decides to override exports, it can create its own command and register and as far as the name matches golem-cli's export implementation will take precedence.

• Command name is the kebab case of the command type name. Just decided to do this, after I gave same name for two commands.

Currently supported commands

• Commands are auto completed, and all options are available once user hits : and keep clicking tab

Examples:

Exports

TypeInfo

Clear

Command Error

If clap::Parser is used to implement the parse function in Command above, help and error documents are automatically. It is upto the client what to use as a parser. Given golem-rib is going to be used in other runtimes soon, its better not to enforce clients who want to add new commands to depend on Clap as such.

The inbuilt commands of golem-rib-repl are using clap for parse and documentations

Command Help

Other fix

• Resources and instances could never be the return value before. This resulted in just compiler errors often. Now we made it flexible by tweaking a bit of interpreter for the benefit of users.
  It's a trade off after thinking and trying out a lot from a user perspective.

Just used record type for now - no other choice

instead of

Load and Unload commands can be supported as part of supporting multiple components properly. It will create more problems to expose these functionalities now, especially from golem-cli

REPL API changes

It breaks compatibility but it's a simple change. Add None for command-registry when creating RibReplConfig