Add missing documentation to transforms module

[rukai]

The transforms module is a core part of our public API, so it should be well documented. This PR adds documentation for many missing fields.

I noticed TransformContextConfig::protocol should really be named TransformContextConfig::up_chain_protocol but I have not renamed it because that would force us into shotover 0.5 so soon after 0.4, so I left a TODO instead.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #1699 will not alter performance

_{Comparing rukai:document_transforms_module (1afa565) with main (580c782)}

Summary

✅ 39 untouched benchmarks