[2.x] Deprecate 'Whitelist' classes in package 'org.opensearch.painless.spi' and create alternative 'Allowlist' classes

[tlfeng]

Description

To support inclusive language, the whitelist terminology is going to be replaced by allowlist in the code base.

Issues Resolved

A part of issue #1683

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/1319/
• CommitID: ef128b7

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/1320/
• CommitID: a9c6e65

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/1324/
• CommitID: 355b748

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/1323/
• CommitID: 6f77583

[codecov-commenter]

Codecov Report

Merging #4101 (6f77583) into 2.x (3bf01e9) will increase coverage by 0.16%.
The diff coverage is 74.12%.

❗ Current head 6f77583 differs from pull request most recent head 50ade46. Consider uploading reports for the commit 50ade46 to get more accurate results

@@             Coverage Diff              @@
##                2.x    #4101      +/-   ##
============================================
+ Coverage     70.45%   70.62%   +0.16%     
- Complexity    56513    56749     +236     
============================================
  Files          4540     4554      +14     
  Lines        272326   272705     +379     
  Branches      40017    40048      +31     
============================================
+ Hits         191860   192587     +727     
+ Misses        64360    64047     -313     
+ Partials      16106    16071      -35     

Impacted Files	Coverage Δ
...a/org/opensearch/gradle/test/DistroTestPlugin.java	0.00% <ø> (ø)
...nsearch/painless/spi/AllowlistInstanceBinding.java	0.00% <0.00%> (ø)
...va/org/opensearch/painless/spi/WhitelistClass.java	100.00% <ø> (ø)
...opensearch/painless/spi/WhitelistClassBinding.java	57.14% <ø> (ø)
...va/org/opensearch/painless/spi/WhitelistField.java	50.00% <ø> (ø)
...nsearch/painless/spi/WhitelistInstanceBinding.java	57.14% <ø> (ø)
...a/org/opensearch/painless/spi/WhitelistMethod.java	100.00% <ø> (ø)
...rg/opensearch/common/settings/ClusterSettings.java	91.89% <ø> (ø)
...index/fielddata/ordinals/GlobalOrdinalMapping.java	77.27% <ø> (ø)
...search/index/fielddata/ordinals/MultiOrdinals.java	60.60% <0.00%> (ø)
... and 528 more

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/1325/
• CommitID: 50ade46

[tlfeng]

After the incomplete attempt to provide alternative allowlist APIs as well as keeping the existing whitelist APIs in this PR, I decided not to deprecate the whitelist APIs before replacing them with allowlist APIs in a future major version.
We will post a plan for the version of removing whitelist APIs. Developers can keep using the existing whitelist APIs till the further notice.

The impact of the plugin developers is likely be minor, if making as breaking change instead of deprecated in advance.
There are 2 plugins (alerting and k-NN) in opensearch-project organization using the whitelist Java APIs, and the affected APIs of them are:

 public Map<ScriptContext<?>, List<Whitelist>> getContextWhitelists()
 -> public Map<ScriptContext<?>, List<Allowlist>> getContextAllowlists()
 
org.opensearch.painless.spi.Whitelist -> Allowlist
org.opensearch.painless.spi.WhitelistLoader -> AllowlistLoader