Deprecate the "Blacklist / Whitelist" nomenclature

[tlfeng]

Is your feature request related to a problem? Please describe.
OpenSearch repository is going to replace the terminology "blacklist / whitelist" with "denylist / allowlist".
issue: opensearch-project/OpenSearch#1483, with the plan for its terminology replacement.

Although the existing usages with "blacklist / whitelist" will be supported in OpenSearch version 2.x until further notice to keep the backwards compatibility, it's suggested to prepare for the nomenclature change in advance, and replace all the usages with "blacklist / whitelist" terminology in the code base.

Describe the solution you'd like
Replace the terminology "blacklist / whitelist" with "denylist / allowlist".

When being compatible with OpenSearch 2.0:

• Replace "whitelist" in code comment and internal method / class name.
• Replace "whitelist" in REST API and Setting
• Replace "whitelist" in documentation

Specifically,

• Impacted REST API: GET (or PUT or PATCH) _plugins/_security/api/whitelist
  Code: https://github.com/opensearch-project/security/blob/1.2.4.0/src/main/java/org/opensearch/security/dlic/rest/api/WhitelistApiAction.java
  Detail: “whitelist” contains in the API endpoint.
• Impacted configuration file: whitelist.yml
  Document: https://www.opensearch.org/docs/1.2/security-plugin/configuration/yaml/#whitelistyml
  Detail: It is a YAML file in plugins/opensearch-security/securityconfig directory, configurations defined in the file can be imported to Security plugin.

Describe alternatives you've considered
None.

Additional context
An existing PR: #1560

[peternied]

Deprecate did not make it in time for the v2.0.0 release, it will be targeted for v2.1.0

[davidlago]

Talked to @cliu123 offline, he is working on this and we are still targeting 2.0 GA.