fix: always define custom element class version getter

[web-padawan]

Description

This fixes an error with version listed as undefined when trying to re-define the same class with a different version:

Tried to define vaadin-iconset version undefined when version 24.5.0-alpha11 is already in use. Something will probably break.
console.error @ (index):5
defineCustomElement @ define.js:23

The issue is a regression from #6568 where I moved the version number from static get version() (always available) to be hardcoded in the defineCustomElement (only available for the first custom element definition).

The fix is to always define a version getter, regardless of whether the custom element is already defined or not.

Type of change

• Bugfix

[sonarqubecloud]

Quality Gate passed

Issues
0 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 SonarCloud

[web-padawan]

Note, I had to move version to an optional parameter because existing tests were using version object field thus making them false-positive (they should have been updated when refactoring logic in #6568).

I don't have better ideas how to mimic the actual case with two copies of the defineCustomElement loaded by the browser. At least with this logic, tests fail if Object.defineProperty is moved back to where it was.