Update newHeader for Snapshot pages

[skumawat2025]

Description

This PR tries to update the new Header for snapshot pages

Issues Resolved

[List any issues this PR will resolve]

Snapshot policy (when newHomePage is off)

1. Snapshot policy list
   
2. Snapshot policy details
   
3. Edit policy
   
4. Create policy
   

Snapshot policy (when newHomePage is on)

1. Snapshot policy list
   
2. Snapshot policy details
   
3. Edit policy
   
4. Create policy
   

Check List

• Commits are signed per the DCO using --signoff

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[SuZhou-Joe]

Perhaps move it to a context state?

[CaptainDredge]

@SuZhou-Joe I'm of the opinion that its better to check for feature flag in main.tsx and pass it as a prop to components, we won't need context since its just a single level prop drilling. Wdyt?

[SuZhou-Joe]

I am just thinking we are copy

const uiSettings = getUISettings();
const useNewUx = uiSettings.get("home:useNewHomePage");

in multiple place, maybe we can consider to move that to a util or somewhere.

[SuZhou-Joe]

The screenshot looks good to me.

[opensearch-trigger-bot]

The backport to 2.x 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/index-management-dashboards-plugin/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/index-management-dashboards-plugin/backport-2.x
# Create a new branch
git switch --create backport/backport-1105-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c486b61345ee3411a6fa9f162180d807d5d9e8ea
# Push it to GitHub
git push --set-upstream origin backport/backport-1105-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/index-management-dashboards-plugin/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-1105-to-2.x.