fix(ui): Add missing mdi-v7 icon set (fix: #14696)

[yusufkandemir]

What kind of change does this PR introduce?

• Bugfix

Does this PR introduce a breaking change?

• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)

Other information:
Resolves #14696.
For v2.
v1 counterpart: #14807

I checked the release notes for mdi-v7, and it doesn't have any changes affecting our icon set. So, content-wise, mdi-v6 and mdi-v7 are the same.

About SVG icon generation:
As the regex is the same(mdi-) for both mdi-v6 and mdi-v7, the previous logic was using the first one matching, i.e. mdi-v6 since it's higher in the list. So, I had to adjust the logic to prioritize the original set being processed.