Export all functions with alpha numeric names from entrypoint module

[paulcadman]

This is part of the implementation for #1419

This PR adds __attribute__((export_name(<name>)) declarations to every type signature corresponding to every symbol in the entry point module that has an alpha numeric name (so that it can safely be present in the output C file). This is an intermediate step to adding the export information to the juvix.yaml file as described in #1419.

This causes these functions to be present in the export table of the resulting WASM module.

To test this we need to be able to invoke the exported functions using the WASM module. This raises the issue of how we will execute these functions in the Anoma VM and (possibly) in the browser. For this use case it is not appropriate to use the WASM-WASI runtime as these IO functions (providing fd_write, fd_read, proc_exit etc.) are not available in the Anoma VM or in the browser.

So this PR also adds a new standalone runtime for the compiler, in addition to the WASI standalone and the WASI libc runtimes. This runtime is appropriate for compiling WASM libraries which export functions that can be invoked without the WASI imports (and that do not, for example, have a main entry point). This is the runtime we'll use for compiling validity predicates for example.

To try this runtime out:

cd tests/positive/MiniC/ExportName
juvix compile --runtime standalone Input.juvix

Then use wasmer to inspect the output WASM file, see it exports all the functions in scope in the module:

wasmer inspect Input.wasm
Type: wasm
Size: 169 B
Imports:
  Functions:
  Memories:
  Tables:
  Globals:
Exports:
  Functions:
    "one": [] -> [I32]
    "two": [] -> [I32]
    "three": [] -> [I32]
    "four": [] -> [I32]
    "five": [] -> [I32]
    "six": [] -> [I32]
    "fun": [] -> [I32]
  Memories:
    "memory": not shared (2 pages..)
  Tables:
  Globals:

We can then invoke the fun function for example:

wasmer run Input.wasm --invoke fun
6

[jonaprieto]

🚢