RFR: 8305321: Remove unused exports in java.desktop

[Daniel Jeliński]

Please review this patch that removes a number of unused exports from java.desktop native libraries.

In most cases I removed JNIEXPORT from methods and variables that are only used within a single shared library. Other than that:
- removed `getSunFontIDs` that was reportedly used by rasterizer; as far as I could tell, rasterizer project is dead now, but if that's incorrect I can restore that export.
- removed `colorValueID` in X11Color; that field was not used.
- removed `J2dTraceInit` from header file. That method is only used internally by `J2dTraceImpl`.

The methods `Transform_GetInfo` and `Transform_transform` are declared in GraphicsPrimitiveMgr, but are only used in TransformHelper. Let me know if I should move them to where they are used.

The method `img_makePalette`, currently located in `share/native/libawt/awt/image/cvutils/img_colors.c`, is only used by `unix/native/common/awt/X11Color.c`; it could be moved to the same directory to avoid exporting the method from libawt. The files `img_colors.[ch]` do not have any references to other files in `cvutils`.

Manually verified that the exports are no longer present after these changes. Tier1-3 and client libs tests still pass.

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Commit messages:
 - Make J2dTraceInit static
 - Remove unnecessary exports

Changes: https://git.openjdk.org/jdk/pull/13261/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13261&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305321
  Stats: 42 lines in 16 files changed: 3 ins; 17 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/13261.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13261/head:pull/13261

PR: https://git.openjdk.org/jdk/pull/13261