Enhance new `jbang export gradle|maven` subcommands

[tadayosi]

PR #1936 will add new subcommands jbang export gradle|maven.

But there are issues to be improved for the subcommands, including:

• [x] They ignore //PREVIEW (https://github.com/jbangdev/jbang/issues/1961)
• [x] They break on kotlin/other languages (https://github.com/jbangdev/jbang/issues/1962)
• [ ] Quarkus integration not handled (so jbang -t qli test.java; jbang export maven test.java doesnt work)
• [ ] Create runnable uber/shadow JARs (https://github.com/jbangdev/jbang/issues/1982)
• And probably more

Originally posted by @maxandersen in https://github.com/jbangdev/jbang/issues/1936#issuecomment-2719362041

[wfouche]

Quarkus integration not handled (so jbang -t qli test.java; jbang export maven test.java doesnt work)

jbang -t qli test.java --> jbang init -t qcli test.java