[rfc][icedtea-web] rust launcher made able to find JRE from path

[Jiri Vanek]

This patch moving jre detection from main to utils.
I addition it is adding ability to scan path, and find jre on it, if the build is *not* distribution
one.

So in extracted method, the affected is:
+                    match os.get_registry_jdk() {
+                        Some(path) => {
+                            os.log("itw-rust-debug: found and using");
+                            return path;
+                        }
+                        None => {
+                            os.log("itw-rust-debug: nothing");
+                            os.log("itw-rust-debug: trying jdk from path");
+                            match get_jdk_from_path_conditionally(os) {
+                                Some(path) => {
+                                    os.log("itw-rust-debug: found and using");
+                                    return path;
+                                }
+                                None => {
+                                    os.log("itw-rust-debug: nothing");
+                                    os.log("itw-rust-debug: failing down to hardcoded");
+                                    return std::path::PathBuf::from(hardcoded_paths::get_jre());
+                                }
+                            }
+                        }
+                    }

where new is
                   match get_jdk_from_path_conditionally(os) {
+                                Some(path) => {
+                                    os.log("itw-rust-debug: found and using");
+                                    return path;
+                                }

Sorry for the included re-factoring.

J.
-- 
Jiri Vanek
Senior QE engineer, OpenJDK QE lead, Mgr.
Red Hat Czech
jvanek at redhat.com    M: +420775390109