[OpenJDK 2D-Dev] RFR: 8259042: Inconsistent use of general primitives loops

[Sergey Bylokhov]

The java2d uses the primitives such as Blit loop for rendering differing things. Currently, not all possible variants of primitives are implemented, but it is possible to register some general loop that may produce the primitives for some specific src/comp/dst.

But we have some inconsistent here:
 - Some primitives register themselves as a general loop but always return null in the makePrimitive() method
 - Some primitives (which are not registered as general loops) return null or throw an error in the makePrimitive() method

After the fix:
 - The primitive will be registered as a general primitive only if it has a meaningful makePrimitive method
 - An attempt to call the makePrimitive for non registered general loop will cause an error

mach5 is green

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Commit messages:
 - Initial fix

Changes: https://git.openjdk.java.net/jdk/pull/1926/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1926&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259042
  Stats: 260 lines in 22 files changed: 33 ins; 167 del; 60 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1926.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1926/head:pull/1926

PR: https://git.openjdk.java.net/jdk/pull/1926