chore: cleanup packages/open-scd and packages/plugins after split

[juancho0202]

I came up with a list of work items put into this massive PR, I hope it helps:

• Added named exports for packages/open-scd
• Extracted scl related foundation files and functions to packages/core
• Updated imports on packages/plugins and packages/open-scd
• Downgraded snowpack to allow esm transpired imports into require statements
• Included root script clean:modules to remove package-lock.json and all node_modules folders
• Updated @typescript-eslint/parser and @typescript-eslint/eslint-plugin to version 7.8.0 in all packages
• Updated tsconfig in both packages/open-scd and packages/plugins and included new tsconfig.build.json files to customise exports and still allow typescript to run in all the code (src and test files)
• Updated web-test-runner config in both packages/open-scd
• Removed deprecated Wizarding and Editing mixins which were being used in tests at packages/open-scd and packages/plugins
• Fixed mock-editor and mock-wizard-editor to use Editor and Wizards addons instead

[trusz]

The changes in the PR seem to be necessary, but it is just too bit. I'd prefer to split it up order the items and solve the conflicts in smaller PRs.