Add module caching

[davejcameron]

Use disk-based caching of compiled modules

By default it stores the files in the following locations

BytecodeAlliance.wasmtime

/// |Platform | Value                                                                 | Example                                             |
/// | ------- | --------------------------------------------------------------------- | --------------------------------------------------- |
/// | Linux   | `$XDG_CACHE_HOME`/`_project_path_` or `$HOME`/.cache/`_project_path_` | /home/alice/.cache/barapp                           |
/// | macOS   | `$HOME`/Library/Caches/`_project_path_`                               | /Users/Alice/Library/Caches/com.Foo-Corp.Bar-App    |
/// | Windows | `{FOLDERID_LocalAppData}`\\`_project_path_`\\cache                    | C:\Users\Alice\AppData\Local\Foo Corp\Bar App\cache |

By default compiled modules are cached for 1 hour.