* Remove ParserParams
ParserParams is only used to record the root of the project, which is
used to prefix source file paths. However source file paths are always
absolute so this is not required.
* Add GetAbsPath to Files effect
The Files effect is not responsible for resolving a relative module
path into an absolute path on disk. This will allow us to resolve
relative module paths to alternative paths, for example to point to the
standard library on disk.
* Files effect getAbsPath returns paths within the registered standard
library
This means that the standard library can exist on disk at a different
location to the Juvix project.
A command line flag --stdlib-path can be specified to point to a
standard library, otherwise the embedded standard library is written to
disk at $PROJ_DIR/.juvix-build/stdlib and this is used instead.
* Recreate stdlib dir only when juvix version changes
* Add UpdateStdlib to the Files effect
* Add comment for stdlibOrFile
* Remove spurious import
