RFR: 8254176: Lanai: MTLTexturePool optimize lookup of expired textures

[Alexey Ushakov]

Do not lookup all the textures to remove not used ones

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

Commit messages:
 - 8254176: Lanai: MTLTexturePool optimize lookup of expired textures

Changes: https://git.openjdk.java.net/lanai/pull/112/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=112&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254176
  Stats: 40 lines in 2 files changed: 27 ins; 1 del; 12 mod
  Patch: https://git.openjdk.java.net/lanai/pull/112.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/112/head:pull/112

PR: https://git.openjdk.java.net/lanai/pull/112