Launcher: Defensive fixes

[mrnoname1000]

Added some checks to the launcher to handle missing HOME, JAVA_HOME, or argument to -{C,e,I,S}

Fixes #8747

[mrnoname1000]

Added some code to parse $JAVA_HOME/release instead of source it, which lets us use $JAVA_RELEASE_VERSION for the AppCDS archive which may be more correct and will handle Graal better

[mrnoname1000]

I think we need to detect whether we found a JAVA_HOME a different way that works without the release file; perhaps $JAVA_HOME/bin/java?

The problem with this is we find JAVA_HOME by trimming /bin/java from the path to java, if we add that back on it will always match

[headius]

@mrnoname1000 Please re-review this... it's been sitting for a few months and I want to make sure it's still valid.

[mrnoname1000]

Weirdly enough the last commit to the launcher in master was less than an hour before the first one in this branch, so no conflicts and everything still looks valid

[headius]

@mrnoname1000 Thanks, merged!