fix naming of extension when doing a developer load

[aalves08]

Summary

Fixes #15858

Occurred changes and/or fixed issues

• fix naming of extension when doing a developer load so that it still works fine and doesn't get "swallowed" by the actual Elemental extension installed (different names, means different cards since it won't pick up the Elemental chart when preparing the data to render the cards)
• add developer load tag
• add unit tests

Technical notes summary

Areas or cases that should be tested

• this can be tested with any extension present on the official extensions repo
• add the official extensions repo https://github.com/rancher/ui-plugin-charts branch main (if it's not present on your Rancher system)

Example for Elemental

• install Elemental 3.0.1 from the official extensions repo
• clone the Elemental repo to your pc https://github.com/rancher/elemental-ui
• yarn install and do a local build of Elemental 3.0.2-rc.1 by doing yarn build-pkg elemental
• serve the built packages locally by doing yarn serve-pkgs
• do a developer load of the locally served Elemental extension into Rancher
• make sure that both cards appear as the screenshots on the installed tab

Areas which could experience regressions

Screenshot/Video

Checklist

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