Add S3 Authentication to Data Source Manager

[rockliffelewis]

Feature description

Since QGIS 3.30 there is support for S3 authentication in the external storage browser (https://github.com/qgis/QGIS/pull/51287)

It would be great if this authentication type was integrated more broadly into QGIS to make it easier to add assets from S3 with differing auth credentials, as well as storing the S3 auth credentials in a secure manner.

This is currently possible with a few different workarounds by either specifying environment variables for the GDAL VSIS3 driver, or setting the GDAL_CONFIG_FILE environment variable and putting the authentication credentials in there (eg. https://gdal.org/user/configoptions.html#gdal-configuration-file).

An example would be adding a raster file from S3, you would first set it to Protocol: HTTP/HTTPS/FTP, put in the full HTTP url to the S3 object you want to add, and then use the authentication UI to set the Access Key, Secret Key, and Region.

Additional context

No response