Add "Open with Google Scholar" and "Open with Semantic Scholar"

[maxyboy232nu]

Closes #12268

Adds Google Scholar and Semantic Scholar search options to the entry table context menu. Each command reuses ExternalLinkCreator to build a sanitised search URL from the selected entry’s title and launches it via the existing NativeDesktop helper. Test cases are provided in ExternalLinkCreatorTest, and are essentially identical to those written for the ShortScience search.

Steps to test

1. Start JabRef with this branch.
2. Create or open a database with at least one entry whose title field is set.
3. Right click on an entry and choose Search Google Scholar – a browser tab should open with the title pre-filled on scholar.google.com.
4. Repeat with Search Semantic Scholar – it should open semanticscholar.org with the correct query.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.

[github-actions]

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[Siedlerchr]

Please move all these three to a new submenu, "Open in...." to not clutter the user interface