Extract non-overridable SystemJvmOptions

[pgomulka]

Description

Some of the jvm options in SystemJvmOptions are not meant to be overridable by a user. We should consider refactoring them into a separate Options class and at least warn when a user is attempting to override them.
One instance of this is "-Djava.locale.providers=SPI,COMPAT",
if a user simply sets this to other value, he will get incorrect date/time calculations (this mostly affects week based date formats).
There might be more settings falling into non-overridable category (log4j settings comes to mind)
Changing values of these should be still ok, but user should be aware that he is doing this on his own responsibility. We don't have test coverage for most of these settings being changed.

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[mosche]

We've discussed this during our sync today

• parsing all the various types of JVM options and system properties is nasty
• coming up with an exhaustive deny list will be tough, there will always be more cases
• an allow list, on the other hand, will likely hurt our ability to troubleshoot / fix issues

A simple approach would be to enforce (set) certain system properties early during node startup, e.g. -Djava.locale.providers, to prevent them from being overwritten. We can easily do this on a case by base basis.