Added wasi for v1 wasmrs components & helper macros.

[jsoverson]

This PR adds WASI support for v1 wasmrs components.

Sample config:

name: 'wasi-fs'
kind: wick/component@v1
metadata:
  version: '0.0.1'
resources:
  - name: ROOT
    resource:
      kind: wick/resource/volume@v1
      path: '{{ctx.root_config.root}}'
component:
  kind: wick/component/wasmrs@v1
  ref: build/component.signed.wasm
  volumes:
    - resource: ROOT
      path: /
  with:
    - name: root
      type: string
  operations:
    - name: read_string
      inputs:
        - name: filename
          type: string
      outputs:
        - name: output
          type: string
    - name: write_string
      inputs:
        - name: filename
          type: string
        - name: contents
          type: string
      outputs:
        - name: bytes_written
          type: int

As part of building the WASI test modules, I included experimental macros and proc_macro attributes for common operation cases. The WASI module showcases them but they're not necessary to rely on or use.

Breaking changes for component devs:

• There was an inconsistency to the naming patterns in wick-component-codegen. Everything generated for operations was housed under individual operation_name::* modules in the generated code, except the operation trait itself which was named [OperationName]Operation. This PR moves the operation trait to operation_name::Operation. To recompile old components, the operation implementations need to be changed from impl OperationNameOperation for Component to impl operation_name::Operation for Component.
• The .error() method on outputs now takes a &str instead of impl AsRef<str> due to becoming a trait methods vs generated code. Any call to .error that passed in a String or otherwise will need to be updated to pass a string slice instead (e.g. outputs.output.error(an_error_string) needs to be changed to outputs.output.error(&an_error_string)