Add direct power trace foundation

[AlCalzone]

This PR adds the acquisition foundation for tinySA support. It builds on the merged geometry, display-capability, and shared-statistics prerequisites in #12, #13, and #14.

sdrtop's acquisition path only supported sample-streaming receivers. Spectrum analyzers that report calibrated power traces had no accurate path into its spectrum and waterfall views.

This PR adds direct power acquisition and compatible display layouts. #8 builds the tinySA backend on this foundation.

[musithang]

Thanks a lot! I'll review it tonight at home, or tomorrow morning at the latest, and then I'll merge it. :)

[AlCalzone]

Three independent preparation drafts now precede the foundation: #12 aligns bin geometry, #13 moves display assumptions into device capabilities, and #14 shares acquisition behavior. After they land, #7 will be rebased onto main; the tinySA sequence then continues through #8, #9, #10, and #11. The corresponding dependent branches remain registered as native stack 4 in the fork because GitHub cannot register cross-fork PRs in an upstream native stack.

[musithang]

Perfect, thanks for structuring it so cleanly!

[AlCalzone]

I'll set it ready for review when I'm done reviewing myself 😅

[musithang]

Sounds good, take your time! Let me know when it's ready. 👍

[AlCalzone]

@musithang sorry for the PR churn. I didn't like how big this PR had gotten after a few local review rounds, so I split out a few things.

#12
#13
#14

are ready for your review now. We'll continue with this one after those are done.

[musithang]

#12, #13, #14 are all merged now. This one's showing conflicts against main since it still carries the same prep commits under different hashes. Go ahead and rebase whenever you're ready, that should drop the duplicates and leave just the actual tinySA foundation. I'll review and test locally again once it's up to date. Let me know when you ready.