Prior to this commit, it was not possible to register the root
directory as a native image resource; however, it is necessary to be
able to register the root directory to enable classpath scanning of the
root directory within a native image -- for example, to support
resource patterns such as `classpath*:/*.properties`.
This commit therefore relaxes the precondition check in the
ResourcePatternHint constructor to allow explicit registration of the
root directory.
Closes gh-29402
d03102edc3