feat: generate PWA icons at build time

[mcollovati]

Description

Generates PWA icons during the production build, preventing the need to use AWT APIs at runtime and making first requests to the application faster. Also prevents potential issues caused by loading AWT native library in native images.
If the base icon cannot be found at build time, Flow will attempt to generate the icons at runtime, exactly how it does before this change.

Fixes #19497

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[github-actions]

Test Results

1 157 files  + 1  1 157 suites  +1   1h 34m 44s ⏱️ + 2m 16s
7 506 tests + 5  7 453 ✅ + 5  53 💤 ±0  0 ❌ ±0 
7 825 runs   - 38  7 762 ✅  - 38  63 💤 ±0  0 ❌ ±0 

Results for commit 8a2faa3. ± Comparison against base commit bd8c796.

♻️ This comment has been updated with latest results.

[sonarcloud]

Quality Gate passed

Issues
27 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud