[Remote] Use .NET options and consolidate environment variables

[kvenkatrajan]

.NET options - appsettings.json + config (env variables)

Not required for Ignite based on discussion with team

CC: @vukelich , @anuchandy

[anuchandy]

Status: Connie did some work that we should look at and decide if we have any follow ups. This is a polish item for the experience of configuring the MCP server. We don't expect users to routinely reconfigure the MCP server.

[srnagar]

This issue tracks the work to replace direct Environment.GetValue calls with configuration-based retrieval, since the configuration system already handles environment variables and other sources.