Implement userscripts cache

[ACTCD]

This idea was initially formed in #424, and we cannot read files in "save location" synchronously due to the asynchronous nature of the "File Provider".

So a good solution is that we cache them in an internal synchronously readable location and synchronize and update asynchronously.

Now let us think further and document this issue.

We should cache the parsed structured data

Compared to the current reading and parsing content from a userscript file every time.
We should cache the parsed metadata object and the separate userscript code.
It can definitely help us reduce calculations, delays, and energy consumption:

• Investigate extension energy consumption anomalies #557
• manifest.json makes no-op changes on disk very frequently #637

Update the cache only if the original file changes are detected.

Going further, we could even minify the userscript code to improve the efficiency of transmission and parsing.
Note that we should provide an option to disable minify or ship sourcemap for user debugging.

The options worth investing in might be:

• https://www.npmjs.com/package/oxc-minify
• oxc is used as build rolldown and will replace rollup and esbuild in the future in vite.

We should also refactor @require to make it pre-bundled and stored in the cache instead of the current way.

Cache location and bundle method

Possible cache locations are the native app container or browser.storage.
We could use the bundler native version in swfit or wasm version in browser.