API calibration for `fuchsia.net.features`

[Bruno Dal Bo]

Hello API council,

I'd like to introduce `fuchsia.net.features` in https://fxrev.dev/888311. Its motivation is to enable boot-time selection between network stack versions (background in go/ns3-sd-food).

Our willing client is cast-agent, using DCS flags to control this platform feature.

I just pushed the simple design up to get the conversation started, given its sole purpose is to be in the SDK for this use case, it made sense to get in touch with the council immediately. Please let me know if I should land this outside of the SDK first and then re-email the council for calibration.

Thank you,
--

Bruno