Support Fields Minus Command

[LantaoJin]

Description

Support fields - <field list> syntax

Check https://opensearch.org/docs/latest/search-plugins/sql/ppl/functions/#syntax-2

Issues Resolved

Resolves #696

Check List

• Updated documentation (ppl-spark-integration/README.md)
• Implemented unit tests
• Implemented tests for combination with other commands
• 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.

[opensearch-trigger-bot]

The backport to 0.5-nexus failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/opensearch-spark/backport-0.5-nexus 0.5-nexus
# Navigate to the new working tree
pushd ../.worktrees/opensearch-spark/backport-0.5-nexus
# Create a new branch
git switch --create backport/backport-698-to-0.5-nexus
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 919ba5ce4c2c7179c1f80508a4672ee685dbced3
# Push it to GitHub
git push --set-upstream origin backport/backport-698-to-0.5-nexus
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/opensearch-spark/backport-0.5-nexus

Then, create a pull request where the base branch is 0.5-nexus and the compare/head branch is backport/backport-698-to-0.5-nexus.