HTML5: Enable mbedTLS module for Crypto object, force disable Asset Library

[akien-mga]

Increases the size of the wasm by around 3% (~300-350 KiB).

This enables using the Crypto object for hashing, signing and encryption,
and therefore reduces the gap between the features of the HTML5 platform
and other platforms.

Closes godotengine/godot-proposals#3574.

[akien-mga]

Also removed the matching notes from the documentation. Didn't test that the features actually work fine yet though.

There's also still a similar note in WebSocketServer but I think this one is due to browser limitations and not mbedTLS? @Faless

[akien-mga]

The Asset Library might need more work to be usable in the Web build, with this PR it's now enabled but spams warnings:

WARNING: HTTPClient polled multiple times in one frame, but request cannot progress more than once per frame on the HTML5 platform. [godot.tools.js:369:18](http://localhost:3000/godot.tools.js)
   at: poll (platform/javascript/http_client_javascript.cpp:270) - HTTPClient polled multiple times in one frame, but request cannot progress more than once per frame on the HTML5 platform. [godot.tools.js:369:18](http://localhost:3000/godot.tools.js)

And it doesn't show any asset.

There are also those two warnings when the asset lib plugin is set up:

WARNING: HTTP proxy feature is not available [godot.tools.js:369:18](http://localhost:3000/godot.tools.js)
   at: set_http_proxy (core/io/http_client.cpp:847) - HTTP proxy feature is not available [godot.tools.js:369:18](http://localhost:3000/godot.tools.js)
WARNING: HTTPS proxy feature is not available [godot.tools.js:369:18](http://localhost:3000/godot.tools.js)
   at: set_https_proxy (core/io/http_client.cpp:861) - HTTPS proxy feature is not available

[Faless]

As mentioned in chat, the asset library cannot work right now because browsers requires CORS which github (where the assets are hosted) do not allow.

To support the asset library in the browsers we would need to either host or mirror the assets somewhere else, allowing CORS (at least from our domain).

[Faless]

There's also still a similar note in WebSocketServer but I think this one is due to browser limitations and not mbedTLS?

Yeah, browsers only have the client API, so there is no way to implement a WebSocketServer there.

[akien-mga]

I added a commit to always disable the Asset Library on HTML5 without relying on the availability of StreamPeerSSL only.

[akien-mga]

Cherry-picked for 3.5.