Make it possible to enable/disable invokedynamic after boot.

* Deprecate loaded-once static values from RubyInstanceConfig.
* Use Option.load everywhere static values were used.
* Move to using released "options" library.
Add a --dev flag that disables our JIT and forces Hotspot tier 1.

Specifying the --dev flag adds the following JVM flags to startup:

-XX:+TieredCompilation
-XX:TieredStopAtLevel=1
-Djruby.compile.mode=OFF
-Djruby.compile.invokedynamic=false
Add --dev flag parts that work after JVM boot.