Dynamically detect newer JavaSE-N execution environments from Installed JREs

Currently, allowing to target JavaSE-N requires that JDT ships support for Java N. However, in some cases, it might not be strictly necessary to get compiler for N in order to target code using library N. The compiler version mostly matters for the source/target release, not so much for the execution environment.
It looks like ExecutionEnvironmentAnalyzer hardcodes the list of possible Java versions. But instead of that, we should consider make it more dynamic and list all the EEs that are known by the IDE, basically all the EEs that are known by the Installed JREs. So for example, if I add a Java installation that tells it's Java 25 (`java -version` returns 25), JDT could automatically list JavaSE-25 as a known Execution Environment; without requiring change in the code.