Use Streams API instead of openpgp/web-stream-tools

[sosnovsky]

          We are currently using the `@openpgp/web-stream-tools` library for streaming because the native Streams API doesn't support functions like `readToEnd`, which is utilized in our project.

We could implement our own readToEnd function instead.

I think we might be able to completely remove the dependency on @openpgp/web-stream-tools.

Would you like me to explore this?

Also, should I address this in the current PR or create a separate one?

Originally posted by @ioanmo226 in #5866 (comment)

[sosnovsky]

This dependency is listed in openpgpjs package.json - https://github.com/openpgpjs/openpgpjs/blob/main/package.json#L71, so probably we can remove it from our package.json and then it'll be used only internally by openpgpjs while we'll be using Streams API, will it work this way?

[sosnovsky]

Then let's stick with @openpgp/web-stream-tools for now, as it seems to be more complicated than I've expected. Thanks for checking!