raco pkg catalog-show: improve error for bad catalog
raco pkg catalog-archive: fix handling of source with no checksum
raco pkg: fix treatmennt of "file://" package sources

A "file://" prefix on a package source needs to be consistently
removed. The new `package-source->path` function does that, so it
should be used to convert a package source to a filesystem path.
fix `collection-file-path` & related for binary package installation

Binary package installation failed in the case of collection
splicing, because module-name resolution via `collection-file-path`
did not check for compiled files along hte search path of
registered collection directories.
rackunit/docs-complete: move to the "racket-index" package

Modules are not supposed to move to different packages, anymore, so
I'm breaking a rule. The problem is that having `rackunit/docs-complete`
in "scribble-lib" made "scribble-lib" depend on "racket-index", and
that's an undesirable dependency. (Installing Scribble shouldn't
force you to have Racket documentation.) I should have noticed
the problem when I moved `setup/xref` to "racket-index", but I missed
it.

As far as I can tell, there's only one package on pkgs.racket-lang.org
that isn't in the main repository and uses `rackunit/docs-index`. The
package doesn't correctly declare its dependencies, anyway.
net/url: add `relative-path->relative-url-string`
pkg/lib: more fixes to handling of relative package sources in catalogs

Relative paths in a catalog should be treated as relative URLs, not
relative paths.
make site: use relative paths in the pkg catalog for a site
raco setup: fix dependency checking and PLTCOMPILEDROOTS

Closes PR 14537
raco setup: fix documentation rebuild for PLTCOMPILEDROOTS
raco pkg: fix conflict checking for PLTCOMPILEDROOTS

The fix is for a corner case that is unlikely to show up,
but the repaired code is simpler.
fix typo in Windows "build.bat"