[CI checking only] Implement unused Lv2UridCache

[JohannesLorenz]

Just refactoring of #5691 .

No review, just CI.

[LmmsBot]

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Linux

• Linux (AppImage): lmms-1.2.3-732%2Bg613d203-linux-x86_64.AppImage (build link)

Windows

• Windows 32-bit: lmms-1.2.3-732%2Bg613d20361-mingw-win32.exe (build link)
• Windows 64-bit: lmms-1.2.3-732%2Bg613d20361-mingw-win64.exe (build link)

macOS

• macOS : lmms-1.2.3-731%2Bg0d89d64f4-mac10.13.dmg (build link)
• macOS : lmms-1.2.3-732%2Bg613d20361-mac10.13.dmg (build link)

🤖

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