Redirect stdout/stderr from tasks into quake for multiplexing

[cassaundra]

At the moment, all tasks output directly to stdout/stderr. Use nushell's streaming capabilities to process task output streams and direct them to a stylized output and/or log.

[cassaundra]

note: having experimented with this in the past, nushell's eval_block (which we currently use) is blocking, making it insuitable for streaming command output when redirecting stdout/stderr. we'd need to re-implement it to (possibly by exposing some externals in the soft fork) to get live RawStreams

[cassaundra]

Somewhat related nushell issue and notes from core team meeting:

• First-class stream type nushell/nushell#10916
• https://hackmd.io/TZsIBlpyQs-GVVwsdCcmQA#Streaming-as-a-first-class-citizen

The solution to this particular issue is unlikely to involve actually implementing user-facing streaming, but refactoring the various eval functions might pave the way for it. There's probably an even simpler hack here too but I'd like nushell to have better pipeline support anyway...