Fix build errors after refactoring of Strings class in core

[Hailong-am]

Description of changes:

Fix build errors after refactoring of Strings class in core
opensearch-project/OpenSearch#7508

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[Hailong-am]

test run on ubuntu-latest failed due to opensearch distribution is not up to date

java.lang.NoClassDefFoundError: org/opensearch/core/common/Strings
» at org.opensearch.commons.authuser.User.parse(User.java:162)

[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-786-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 30e16d999d18e0001c8963794f8fcef5eb3c6e80
# Push it to GitHub
git push --set-upstream origin backport/backport-786-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-786-to-2.x.

[Hailong-am]

#845