The user expects the editor to remember the positions of fields they
navigated from to a new level, so when they return they get put in the
same spot.
We push the index from one field into every level of the value.
Unfortunately this introduces pointers and all the woes they bring.
Change-Id: I889c28b71fd7082b765e1d6874faeb1b36dade60
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2866
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>
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