With support for multiple contexts we are adding some caching to the whitelist to keep the memory footprint for definitions from exploding.

* master:
  Use Gradle wrapper when building BWC
  Painless: Add a simple cache for whitelist methods and fields. (elastic#28142)
  Fix upgrading indices which use a custom similarity plugin. (elastic#26985)
  Fix Licenses values for CDDL and Custom URL (elastic#27999)
  Cleanup TcpChannelFactory and remove classes (elastic#28102)
  Fix expected plugins test for transport-nio
  [Docs] Fix Date Math example descriptions (elastic#28125)
  Fail rollover if duplicated alias found in template (elastic#28110)
  Avoid concurrent snapshot finalizations when deleting an INIT snapshot (elastic#28078)
  Deprecate `isShardsAcked()` in favour of `isShardsAcknowledged()` (elastic#27819)
  [TEST] Wait for replicas to be allocated before shrinking
  Use the underlying connection version for CCS connections  (elastic#28093)
  test: do not use asn fields
  Test: Add assumeFalse for test that cannot pass on windows
  Clarify reproduce info on Windows
  Remove out-of-date projectile file

* master: (27 commits)
  Declare empty package dirs as output dirs
  Consistent updates of IndexShardSnapshotStatus (elastic#28130)
  Fix Gradle wrapper usage on Windows when building BWC (elastic#28146)
  [Docs] Fix some typos in comments (elastic#28098)
  Use Gradle wrapper when building BWC
  Painless: Add a simple cache for whitelist methods and fields. (elastic#28142)
  Fix upgrading indices which use a custom similarity plugin. (elastic#26985)
  Fix Licenses values for CDDL and Custom URL (elastic#27999)
  Cleanup TcpChannelFactory and remove classes (elastic#28102)
  Fix expected plugins test for transport-nio
  [Docs] Fix Date Math example descriptions (elastic#28125)
  Fail rollover if duplicated alias found in template (elastic#28110)
  Avoid concurrent snapshot finalizations when deleting an INIT snapshot (elastic#28078)
  Deprecate `isShardsAcked()` in favour of `isShardsAcknowledged()` (elastic#27819)
  [TEST] Wait for replicas to be allocated before shrinking
  Use the underlying connection version for CCS connections  (elastic#28093)
  test: do not use asn fields
  Test: Add assumeFalse for test that cannot pass on windows
  Clarify reproduce info on Windows
  Remove out-of-date projectile file
  ...