Refactor and add framework for native jfr event support

[zhengyu123]

This PR replaces PR#3746

• Split JFR package into hosted (com.oracle.svm.hosted.jdk11.jfr) and core (com.oracle.svm.core.jdk11.jfr)
• Add package com.oracle.svm.core.jfr for native jfr event support (e.g. GC events)
• There will no-op JfrEventSupport for jdk8, but a concrete implementation for jdk11 or later
• Remove com.oracle.svm.jfr package

[jerboaa]

@zhengyu123 If you rebase this onto latest master, it should pass all the public gate tests.

[christianhaeubl]

I think it would be better to have the JFR implementation (and its dependencies) in a separate project. Pretty much all VM-internal events should use the JfrNativeEventWriter anyways (via some JDK-independent abstraction).

[christianhaeubl]

I will merge the PR #3720 first, as it is more complex than this PR. After that, I will merge this PR and as part of that process, I am also going to take care of all the conflicts that may come up. So, there is no need on your end to rebase this PR.

[jiekang]

@christianhaeubl Hi Christian! Any updates on this area?

[christianhaeubl]

@jiekang I would like to wait with this until the JDK 8 support is removed from Native Image as the JFR refactoring will be far simpler afterwards. The removal of the JDK 8 support is currently work in progress and should be finished soon.

[christianhaeubl]

I am closing this PR as I merged my PR in the meanwhile. Most JFR-related files are now part of the project com.oracle.svm.core and can therefore be used easily in other Native Image projects (e.g., in the GC).