Provide categorized example structures.

[superstar54]

Fix #1018

[x] Provide categorized example structures, and only the respective examples are shown when the button is clicked.

• Simple crystals
• XPS examples
• XAS examples

[x] The example catalog is extensible by the plugins.
[x] For the "Simple crystals" tab, replace the current ones with the following list (IMPORTANT: remove the string
[x] Remove the "Primitive cell" from everywhere, as done below, as we should always ONLY provide the primitive cell):

• Bulk silicon
• Diamond
• Gallium arsenide
• Gold
• LiCoO2
• Nickel
• Silicon oxide

[x] For gold, replace the current one with its primitive cell.
[x] For Cobalt, remove it and replace with Nickel FCC.

Note for the Silicon oxide: I keep the alpha quartz because Silicon oxide has many possible structures, and it's important to tell which one we are using.

[codecov]

Codecov Report

Attention: Patch coverage is 52.00000% with 12 lines in your changes missing coverage. Please review.

Project coverage is 68.80%. Comparing base (d4c495e) to head (f68f4c9).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/aiidalab_qe/common/widgets.py	30.76%	9 Missing ⚠️
src/aiidalab_qe/app/structure/__init__.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1019      +/-   ##
==========================================
- Coverage   68.86%   68.80%   -0.06%     
==========================================
  Files         115      117       +2     
  Lines        6462     6486      +24     
==========================================
+ Hits         4450     4463      +13     
- Misses       2012     2023      +11     

Flag	Coverage Δ
python-3.11	68.79% <52.00%> (-0.07%)	⬇️
python-3.9	68.83% <52.00%> (-0.06%)	⬇️

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[edan-bainglass]

LGTM @superstar54. Note that the new widget is not MVC compatible and will load on initialization. We're trying to avoid this. We should consider revisiting later (that is, if we don't go the React/Solara way). But for now, the widget is small enough that it should add much of an impact.

[superstar54]

Note that the new widget is not MVC compatible and will load on initialization.

The widget CategorizedStructureExamplesWidget is inherited from StructureExamplesWidget, which is from aiidalab-widget-base, that's why I didn't use MVC. We need to refactor the aiidalab-widget-base using MVC, but in the future.