New partial updates logging APIs

[teh-cmc]

We want to offer newer & nicer ergonomic partial update APIs on the logging side (Python, Rust, C++), something like this:

rr.set_time_sequence("frame", 42)
rr.log("points", rr.Points3D([[0, 0, 0], [1, 1, 1]], colors=[255, 0, 0]))

rr.set_time_sequence("frame", 43)
rr.log("points", [rr.Points3D.components(colors=[0, 0, 255])]) # gets properly tagged

• This is a subset of the larger proposal in Allow archetypes to clear and/or update existing components #3381.

We want this for two reasons:

• Finally make partial updates ergonomic.
• Unblock tagged components.

Complete rationale can be found in #3381 (comment).

[nikolausWest]

I'd love it if the last line could be

rr.log("points",` rr.Points3D.components(colors=[0, 0, 255])) # gets properly tagged

instead of

rr.log("points",` [rr.Points3D.components(colors=[0, 0, 255])]) # gets properly tagged

(i.e. don't require wrapping in a list)

[nikolausWest]

I think we also talked about going with .fields() instead of .components() but I don't remember the conclusion