[foreign-jextract] RFR: 8248560: Specify the behaviour of the ForeignLinker returned by CSupport::getSystemLinker (jextract part)

[Jorn Vernee]

Hi,

This PR contains the fixes needed for foreign-jextract branch after the refactor done by:
https://github.com/openjdk/panama-foreign/pull/327

This is mostly just a mechanical renaming from CSupport to CLinker.

The exception is that ClassConstantHelper had to be re-written to replace dynamic constants of ValueLayouts by
references to the internal ABI classification fields, since they can not be references from generated code, resolving
the current dynamic constants would result in an access error, but the static final constant fields in CLinker are
freely accessible.

Also, since the platform specific constants are no longer publicly visible, jextract will generate classes that
reference the layout constants for the current platform instead of a specific one.

Thanks,
Jorn

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Commit messages:
 - Rename CanonicalField to CanonicalABIType
 - Fix whitespace errors
 - CLinker jextract fixes

Changes: https://git.openjdk.java.net/panama-foreign/pull/329/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=329&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8248560
  Stats: 409 lines in 34 files changed: 187 ins; 76 del; 146 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/329.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/329/head:pull/329

PR: https://git.openjdk.java.net/panama-foreign/pull/329