use script mvnd.{sh,cmd} as default entrypoint

After implementing [the fallback logic](#717 ) in the scripts (`mvnd.{sh,cmd}`), there are some options to change the default entrypoint:

1. alway use script as default entrypoint, and rename native images to `mvnd-native-*`, then one can always use same path to invoke the mvnd on both systems with and without the native image support, whereas the script and detecting logic has [performance penalties](https://github.com/apache/maven-mvnd/pull/717#issuecomment-1377600565).
2. as [@ppalaga suggests](https://github.com/apache/maven-mvnd/pull/717#issuecomment-1378032665), keep the current layout for `bin/` directory, and provide install scripts that replace the native mvnd with a shell script if the native mvnd does not work on or does not match the current platform.

Start by reading the mvnd.{sh,cmd} scripts and the fallback logic in issue #717, then compare the two entrypoint options described here. Done means an agreed and implemented default entrypoint strategy that works for systems with and without native image support.

Written by the indexing model from the issue text.