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