Add TX amplifier

[mossmann]

See mainboard block diagram: https://github.com/greatscottgadgets/lab-notes/tree/main/project-reports/2023-06-02-urti-progress-report#mainboard-block-diagram

This could be a single component with an externally switched bypass path, similar to the design in HackRF One, at least for the initial implementation.

We'll likely want to test candidate components to measure performance on our stack-up over our wide range of operating frequencies.

We will want to be able to guarantee the capability of achieving a certain output power, perhaps 0 dBm, across the whole frequency range.

We might consider two or more separate amplifiers for different frequency ranges. Another option might be a single wideband amplifier plus a secondary (chained) amplifier used only for high frequencies.