Indentifier tool vsicurl support

[Wieschie]

Purpose

• This pull request modifies the IdentifierTool to add support for remote virtual layers through GDAL's vsicurl.

Proposed Changes

• [CHANGE] Add special case handling for /vsicurl/ URLs to IdentifierTool. The 'getbands' API already fully supports this, so all that's needed is for the frontend to provide the proper URL.
• [CHANGE] (optional): During testing, I noticed that the 'getbands' and 'getprofile' API endpoints return an empty 200 response if there is an error inside the script or invalid parameters are provided. I modified these to return a 400 and log the error if one occurs.

Testing

I've tested this PR with our local development environment. We have a WMS server that serves floating point geotiffs, and I created a gdal_wms.xml remote layer description file. The following simple Identifier Tool config works to retrieve point values from the remote layer.

{
    "layer_name": {
        "url": "/vsicurl/https://mapserver/static/gdal_wms.xml",
        "bands": 1,
    }
}

[tariqksoliman]

Awesome and thank you!