Improve error handling around ert3 initialization

[verveerpj]

Issue
Resolves #2760

Approach

• Add error handling for the case that ert3 init fails to connect to the storage.
• Add error handling for the case that ert3 tries to use a storage that not has been initialized properly.

Pre review checklist

• Added appropriate labels

Adding labels helps the maintainers when writing release notes, see sections and the
corresponding labels here: https://github.com/equinor/ert/blob/main/.github/release.yml

[sondreso]

Looks good! Only two minor comments

[codecov-commenter]

Codecov Report

Merging #2779 (f976dcd) into main (f20fec4) will decrease coverage by 0.01%.
The diff coverage is 64.28%.

@@            Coverage Diff             @@
##             main    #2779      +/-   ##
==========================================
- Coverage   65.20%   65.19%   -0.02%     
==========================================
  Files         652      652              
  Lines       53630    53643      +13     
  Branches     4818     4818              
==========================================
  Hits        34970    34970              
- Misses      17058    17067       +9     
- Partials     1602     1606       +4     

Impacted Files	Coverage Δ
ert/storage/__init__.py	100.00% <ø> (ø)
ert3/console/_console.py	88.29% <40.00%> (-1.26%)	⬇️
ert3/workspace/_workspace.py	89.24% <66.66%> (-0.76%)	⬇️
ert/storage/_storage.py	88.85% <83.33%> (-0.10%)	⬇️
libres/lib/res_util/arg_pack.cpp	59.78% <0.00%> (-1.06%)	⬇️
ert_gui/simulation/run_dialog.py	75.70% <0.00%> (-0.71%)	⬇️
libres/lib/enkf/gen_kw.cpp	59.02% <0.00%> (-0.49%)	⬇️
libres/lib/res_util/matrix.cpp	65.40% <0.00%> (-0.28%)	⬇️
libres/lib/enkf/enkf_node.cpp	52.16% <0.00%> (-0.26%)	⬇️
libres/lib/res_util/block_fs.cpp	53.97% <0.00%> (ø)

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[sondreso]

Nice work!