Ark: Variable pane can't compute the size in presence of immediate bindings

[lionel-]

Describe the issue:

The variable pane computes the size of objects in the global environments. If those objects contain environments with "immediate bindings", the size computation fails with a warning in the Ark logs.

See the parent issue #4686 and the investigation notes in #4686 (comment). See also the issue in lobstr, from which we pulled our size computation routine: r-lib/lobstr#48

Steps to reproduce the issue:

Run this in the R console:

library(brms)
m <- brm(bf(mpg ~ hp + (1 | cyl), sigma ~ cyl), data = mtcars, seed = 123)

Expected or desired behavior:

No warning in the logs:

[R]   2024-09-17T09:34:59.797038Z  WARN  Can't compute size of object: bad binding access

And the model m should have a non-zero size when the variable pane is sorted by size:

[petetronic]

I was able to reproduce this issue, sending to Triage.