fix: asset name parsing in static converter

[KristinAoki]

Description

This PR fixes images not loading in the visual text and problem editor. When assets were loaded with asset-v1:org+number+run+type@asset+block/image_name.png asset format, it would incorrectly parse to asset-v1:org+number+run+type@asset+block/asset-v1:org+number+run+type@asset+block@image_name.png. A similar issue was fixed in #497. The same src parser is now used for replaceStaticWithAsset as was added for setAssetToStaticUrl.

Testing

1. Open an html block
2. Add an image
3. Click the "HTML" button in the toolbar
4. Replace the second "@" with "/"
5. Click "Save"
6. Confirm that the image is still visible

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.92%. Comparing base (b68257e) to head (3e89706).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #501   +/-   ##
=======================================
  Coverage   88.91%   88.92%           
=======================================
  Files         248      248           
  Lines        4554     4558    +4     
  Branches      943      944    +1     
=======================================
+ Hits         4049     4053    +4     
  Misses        472      472           
  Partials       33       33           

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[rayzhou-bit]

lgtm