👋🏽  howdy, team!

I highly value the content on this [Data Tiers](https://www.elastic.co/guide/en/elasticsearch/reference/current/data-tiers.html) page. Thanks for writing it! In my experience, some users may become slightly confused by its golden nuggets due to its brevity. This PR attempts to flush out common questions while remaining concise. 

The main changes are in the first and second-to-last sections; however, I do attempt some heading restructuring to make the TOC idea-groupings more clear for easier scan-throughs. 

The specific clarifications I'd like to push in order of appearance:

- There's content tier (for "data category" > "content" as we've dubbed it on the higher page) and the data temperature tiers (for time series). That the temperature tiers group together is technically not stated so users end up asking about when they'd go hot>warm vs content>warm, etc. I suspect this confusion is only because users come straight to this page instead of starting at the hierarchy-parent page so have linked up. 
- (Main) Frozen being accessed/searched "rarely" should imply, well rarely. I wrote 1% in the PR `[TIP]` guideline section as a discussion starting point. Frequently we see users not understanding either that they actually have been or that they shouldn't have ≥25% of all searches hitting frozen tier. This comes up because of architecture bugs (e.g. frozen indices with future timestamps) but also just happenstance (e.g. 01605242 where of searches they hit majority hot, ~5% cold, but then again hit 75% frozen).
- There's a slew of "how do I check that?", "how do I change that (at creation/later)?", "what if I set it null?" questions we get about `_tier_preference` so just extended the existing section already about it. 

TIA! 🙏

Co-authored-by: shainaraskas <58563081+shainaraskas@users.noreply.github.com>

Co-authored-by: shainaraskas <58563081+shainaraskas@users.noreply.github.com>

Co-authored-by: shainaraskas <58563081+shainaraskas@users.noreply.github.com>

Co-authored-by: shainaraskas <58563081+shainaraskas@users.noreply.github.com>

Co-authored-by: Lee Hinman <dakrone@users.noreply.github.com>