Store already added node viewer and load it when needed

[superstar54]

In aiidalab-widgets-base/viewer.py, it creates a new viewer every time we select a new AiiDA node, and the viewer is not saved in the app, so we can not reuse it later. This has two drawbacks:

• The performance is back. user needs to wait every time when selecting a new node.
• One can not call the viewer later, e.g., for reset.

This PR stores the already added viewer and reuses it later.

[codecov]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (7549dab) 80.73% compared to head (d7db9ec) 80.50%.

Files	Patch %	Lines
src/aiidalab_qe/app/result/__init__.py	28.57%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #560      +/-   ##
==========================================
- Coverage   80.73%   80.50%   -0.24%     
==========================================
  Files          49       49              
  Lines        3415     3426      +11     
==========================================
+ Hits         2757     2758       +1     
- Misses        658      668      +10     

Flag	Coverage Δ
python-3.10	80.50% <28.57%> (-0.24%)	⬇️
python-3.8	80.54% <28.57%> (-0.24%)	⬇️
python-3.9	80.54% <28.57%> (-0.24%)	⬇️

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[unkcpz]

@superstar54 this is ready for review? Can you update the PR.

For the performance, can you give it a benchmark?

[superstar54]

Will create another PR from my forked repo.