fix(module:alert): Change span to div when applicable for better responsive experience

[anddrzejb]

🤔 This is a ...

• New feature
• Bug fix
• Site / documentation update
• Demo update
• Component style update
• Bundle size optimization
• Performance optimization
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

💡 Background and solution

<Alert> in react ant-design is based on <div> elements while in ant-design-blazor is based on <span> elements, what causes this type of behaviour when resized:

Notice that also close button is not visible for closable alert.
Also gif demo:

The fix proposed by this PR is bringing the design directly in line with react ant-design:

1. Wrap all previous <span> elements with extra <div class="ant-alert-content"> element
2. Replace all <span> with <div> elements.
   New behaviour after changes:
   

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• Changelog is provided or not needed

[codecov-io]

Codecov Report

Merging #990 (30f18cf) into master (86afda3) will not change coverage.
The diff coverage is 0.00%.

@@          Coverage Diff           @@
##           master    #990   +/-   ##
======================================
  Coverage    5.73%   5.73%           
======================================
  Files         406     406           
  Lines       21823   21823           
======================================
  Hits         1252    1252           
  Misses      20571   20571           

Impacted Files	Coverage Δ
components/alert/Alert.razor	0.00% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 86afda3...30f18cf. Read the comment docs.