Add stored fields for knn_vector type

[jmazanec15]

Description

Fixes bug where we were not creating stored field type for knn_vector even when the mapping parameter is passed. To do this, we create a stored field from the bytes of the vectors. Then, implemented valueForDisplay in order to ensure that the vectors are displayed properly.

Example:

Request:
{
  "stored_fields": ["test_vector"],
  "query": {
    "match_all": {}
  }
}

Response:
{
  "took":248,
  "timed_out":false,
  "_shards":{
    "total":1,
    "successful":1,
    "skipped":0,
    "failed":0
  },
  "hits":{
    "total":{
      "value":1,
      "relation":"eq"
    },
    "max_score":1.0,
    "hits":[
      {
        "_index":"test_index",
        "_id":"1",
        "_score":1.0,
        "fields":{"test_vector":[[-128,0,1,127]]}
      }
    ]
  }
}

Along with this, clean up the field mapper implementations.

Add relevant uTs and iTs to ensure functionality is working as expected.

Issues Resolved

#1606

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed as 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.

[jmazanec15]

changed these to use built ins to clean up the code.

[jmazanec15]

Removed as it is default for ParametrizedFieldMapper

[jmazanec15]

@luyuncheng could you take a look at this PR?

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.x 2.x
# Navigate to the new working tree
cd .worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-1630-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 699510d61dd8c583653118be172fb60a00463760
# Push it to GitHub
git push --set-upstream origin backport/backport-1630-to-2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-1630-to-2.x.

[opensearch-trigger-bot]

The backport to 2.13 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.13 2.13
# Navigate to the new working tree
cd .worktrees/backport-2.13
# Create a new branch
git switch --create backport/backport-1630-to-2.13
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 699510d61dd8c583653118be172fb60a00463760
# Push it to GitHub
git push --set-upstream origin backport/backport-1630-to-2.13
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.13

Then, create a pull request where the base branch is 2.13 and the compare/head branch is backport/backport-1630-to-2.13.