`RecordingStream` objects are no longer isolated

[jleibs]

Simple repro:

import rerun as rr

rec1 = rr.RecordingStream("rerun_example", recording_id="episode42")
rec1.log("/small_data", rr.TextLog("Small data -- send it to the viewer"))
rec1.spawn()

rec2 = rr.RecordingStream("rerun_example", recording_id="episode42")
rec2.log("/big_data", rr.TextLog("Big data -- send it to a file"))
rec2.save("big_data.rrd")

Expected Behavior

• /small_data should end up in the viewer
• /big_data should end up in the .rrd file

When opening big_data.rrd later, it is merged into the recording, correctly.

This works as expected in 0.23.

Regression

• All data is sent to the viewer