To aid with discoverability of the temp folder. Note that the directory is explicitly _not_ logged (e.g., `trace!`) to avoid logging sensitive data (e.g., user names)

Co-Authored-By: Ricky Taylor <262786+ricky26@users.noreply.github.com>

Allows configuration of the temp directory after startup, and the retrieval of the `Path` for 3rd party use.

Initial support for WASM `temp://` using OPFS.

Split out certain utility methods which are more general WASM items.

Co-Authored-By: Ricky Taylor <262786+ricky26@users.noreply.github.com>