Integrated: 8256683: Lanai: NetBeans IDE - AA Text rendering appears brighter compared to OpenGL

[Jayathirth D V]

This fix resolves blending issues that we are seeing while drawing grayscale text at many places.
Also it reverts change done in JDK-8242950 to save memory and computation cycles.

-------------

Commit messages:
 - Refactor shader to remove warning
 - Dont override Texture AA state for text rendering
 - Use alpha channel for weight and remove RGBA cache
 - 8256683: Lanai: NetBeans IDE - AA Text rendering appears brighter compared to OpenGL

Changes: https://git.openjdk.java.net/lanai/pull/141/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=141&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256683
  Stats: 67 lines in 8 files changed: 36 ins; 20 del; 11 mod
  Patch: https://git.openjdk.java.net/lanai/pull/141.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/141/head:pull/141

PR: https://git.openjdk.java.net/lanai/pull/141