[Type Removal] Remove TypeFieldMapper usage, remove support of _type in searches and from LeafFieldsLookup

[dreamer-89]

Description

This change introduces following changes:

1. Remove usages of TypeFieldMapper class. In order to keep changes limited, retained TypeFieldMapper class which is referred in multiple tests for storing nested paths. Once, [Remove] Type from nested fields using new metadata field mapper #3004 is merged; this class can be removed completely.
2. Remove _type support in searches. Bug [BUG] _type value in field of exists query returns all records #2989
3. Remove type handling in LeafFieldsLookup

Issues Resolved

#2989

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.

[dreamer-89]

Getting issues with gradle on ubuntu machine. Tried stopping/starting gradle but it didn't help.

ubuntu@ip-172-31-33-23:~/OpenSearch$ ./gradlew start

> Configure project :qa:os
Cannot add task 'destructiveDistroTest.docker' as a task with that name already exists.
=======================================
OpenSearch Build Hamster says Hello!
  Gradle Version        : 7.4.2
  OS Info               : Linux 5.13.0-1019-aws (amd64)
  Runtime JDK Version   : 17 (Eclipse Temurin JDK)
  Runtime java.home     : /home/ubuntu/sw/jdk-17.0.1+12
  Gradle JDK Version    : 17 (Eclipse Temurin JDK)
  Gradle java.home      : /home/ubuntu/sw/jdk-17.0.1+12
  Random Testing Seed   : 3B2F9F522B14152D
  In FIPS 140 mode      : false
=======================================

FAILURE: Build completed with 4 failures.

1: Task failed with an exception.
-----------
* What went wrong:
Gradle could not start your build.
> Cannot create service of type TaskExecuter using method ProjectExecutionServices.createTaskExecuter() as there is a problem with parameter #14 of type ReservedFileSystemLocationRegistry.
   > Cannot create service of type ReservedFileSystemLocationRegistry using method ProjectExecutionServices.createReservedFileLocationRegistry() as there is a problem with parameter #1 of type List<ReservedFileSystemLocation>.
      > Could not create service of type ExecutionHistoryStore using ExecutionGradleServices.createExecutionHistoryStore().
         > Cannot lock execution history cache (/home/ubuntu/OpenSearch/.gradle/7.4.2/executionHistory) as it has already been locked by this process.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
==============================================================================

[dreamer-89]

start gradle check

[opensearch-ci-bot]

✅   Gradle Check success ccfbf09
Log 4657

Reports 4657

[opensearch-ci-bot]

✅   Gradle Check success ccfbf09
Log 4658

Reports 4658

[nknize]

This is great! LGTM!

[CEHENKLE]

Since we're about to cut rc-1, I'd like to hold on backporting this to 2.0. But really looking forward to getting it into 2.0!

[nknize]

I'd like to hold on backporting this to 2.0.

++ We'll have the PR auto opened but block the merge to prevent it from going in prematurely.