TPC script runtime config extending is broken

[harlan-zw]

Since we're using custom keys for TPC users won't be able to provide config as per the docs and all other scripts.

For example, the NUXT_PUBLIC_SCRIPTS_GOOGLE_TAG_MANAGER_ID key should just work. It doesn't because the key is set to gtm

export default defineNuxtConfig({
  runtimeConfig: {
    public: {
      scripts: {
        googleTagManager: {
          id: '', // NUXT_PUBLIC_SCRIPTS_GOOGLE_TAG_MANAGER_ID
        },
      },
    },
  },
})