DOCS-8240 Add Tag Explorer Documentation

[alai97]

What does this PR do? What is the motivation?

Adds a doc page about the Tag Explorer in the Cloud Cost Management section.

Merge instructions

• [x] Please merge after reviewing

Additional notes

[github-actions[bot]]

Preview links (active after the build_preview check completes)

New or renamed files

• https://docs-staging.datadoghq.com/alai97/add-search-for-cloud-cost-tags/cloud_cost_management/tag_explorer/

[goeln]

Hey @alai97 ! I know we paused this because we were going to make some changes, those changes are now in progress, will keep you up to date

[goeln]

Overall looks good, can we take the screenshots from the demo org? for any cost providers that aren't showing up in demo org, can we truncate the screenshot to just show tags that have a description? the rest of the tags in org 2 i'd rather not have in public docs :)

[goeln]

also, all integrations are now public beta if you can update these docs tor reflect that!!