[foreign-preview] RFR: 8280527: Move jdk.incubator.foreign to java.lang.foreign

[Julia Boes]

On Mon, 24 Jan 2022 19:30:51 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> To prepare for preview, this change removes the jdk.incubator.foreign module and moves the public classes to java.base/java.lang.foreign, implementation classes to java.base/jdk.internal.foreign respectively. 
>> 
>> While here, `SystemLookup` is replaced with the method `ClassLoader::findNative` and the methods in `MemoryHandles` are moved to `MethodHandles`. The `@PreviewFeature(feature=PreviewFeature.Feature.FOREIGN)` annotation and the `--enable-preview` flag are added were needed.
>
> test/jdk/java/foreign/virtual/TestVirtualCalls.java line 60:
> 
>> 58:         funcA = TestVirtualCalls.class.getClassLoader().findNative("funcA").get();
>> 59:         funcB = TestVirtualCalls.class.getClassLoader().findNative("funcB").get();
>> 60:         funcC = TestVirtualCalls.class.getClassLoader().findNative("funcC").get();
> 
> Maybe a helper method could be added to `NativeTestHelper`, like `findNativeOrThrow(...)` to make lookups a little bit simpler in the tests

good idea, I'll add that.

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PR: https://git.openjdk.java.net/panama-foreign/pull/633