IPython console widget size changes on startup if vertical panes are combined

Description

What steps will reproduce the problem?

Beginning with a clean Spyder configuration

1. Open two vertical pane widgets, i.g. Outline and Project
2. Restart Spyder: notice that IPython console height remains unchanged
3. Combine both vertical pane widgets
4. Restart Spyder: notice that IPython console height is reduced
5. Restart Spyder: notice that IPython console height is reduced further
6. This continues until a minimum allowed height is achieved.

Versions

• Spyder version: 5.4.0.dev0 (9e341c0d)
• Python version: 3.9.5
• Qt version: 5.15.2
• PyQt5 version: 5.15.6
• Operating System: Darwin 20.6.0

Dependencies

# Mandatory:
applaunchservices >=0.1.7            :  0.3.0 (OK)
atomicwrites >=1.2.0                 :  1.4.0 (OK)
chardet >=2.0.0                      :  4.0.0 (OK)
cloudpickle >=0.5.0                  :  2.0.0 (OK)
cookiecutter >=1.6.0                 :  1.7.3 (OK)
diff_match_patch >=20181111          :  20200713 (OK)
intervaltree >=3.0.2                 :  3.1.0 (OK)
IPython >=7.31.1;<8.0.0              :  7.33.0 (OK)
jedi >=0.17.2;<0.19.0                :  0.18.1 (OK)
jellyfish >=0.7                      :  0.9.0 (OK)
jsonschema >=3.2.0                   :  4.5.1 (OK)
keyring >=17.0.0                     :  23.5.0 (OK)
nbconvert >=4.0                      :  6.5.0 (OK)
numpydoc >=0.6.0                     :  1.3.1 (OK)
parso >=0.7.0;<0.9.0                 :  0.8.3 (OK)
pexpect >=4.4.0                      :  4.8.0 (OK)
pickleshare >=0.4                    :  0.7.5 (OK)
psutil >=5.3                         :  5.9.0 (OK)
pygments >=2.0                       :  2.12.0 (OK)
pylint >=2.5.0                       :  2.13.8 (OK)
pyls_spyder >=0.4.0                  :  0.4.0 (OK)
pylsp >=1.4.1;<1.5.0                 :  1.4.1 (OK)
pylsp_black >=1.2.0                  :  1.2.1 (OK)
qdarkstyle >=3.0.2;<3.1.0            :  3.0.3 (OK)
qstylizer >=0.1.10                   :  0.2.1 (OK)
qtawesome >=1.0.2                    :  1.1.1 (OK)
qtconsole >=5.3.0;<5.4.0             :  5.4.0.dev0 (OK)
qtpy >=2.1.0                         :  2.1.0 (OK)
rtree >=0.9.7                        :  1.0.0 (OK)
setuptools >=49.6.0                  :  62.2.0 (OK)
sphinx >=0.6.6                       :  4.5.0 (OK)
spyder_kernels >=2.3.0;<2.4.0        :  2.4.0.dev0 (OK)
textdistance >=4.2.0                 :  4.2.2 (OK)
three_merge >=0.1.1                  :  0.1.1 (OK)
watchdog >=0.10.3                    :  2.1.7 (OK)
zmq >=17                             :  22.3.0 (OK)

# Optional:
cython >=0.21                        :  None (NOK)
matplotlib >=3.0.0                   :  None (NOK)
numpy >=1.7                          :  None (NOK)
pandas >=1.1.1                       :  None (NOK)
scipy >=0.17.0                       :  None (NOK)
sympy >=0.7.3                        :  None (NOK)

# Spyder plugins:
spyder_terminal.terminalplugin 1.2.2 :  1.2.2 (OK)

[mrclary]

Just in case, checking on Windows I was able to experience an even stranger behavior. For me the panes on the first vertical space get also a lot of horizontal space:

Although not shown in my original gif posted, I also see this at times on macOS.

[dalthviz]

Just in case, checking on Windows I was able to experience an even stranger behavior. For me the panes on the first vertical space get also a lot of horizontal space: