Add support for extension private deps

[jtreminio]

The way this works for me is, in my extension's .csproj file:

  <ItemGroup>
    <Reference Include="ComfyTyped">
      <HintPath>lib/ComfyTyped.dll</HintPath>
    </Reference>
  </ItemGroup>

I've added the ComfyTyped dep to two of my extensions, one with it fully baked in and used, the other with a very small footprint, swarmui builds fine.

This PR's purpose is for each extension to define its own private dependency, where ExtensionA and ExtensionB both depend on LibA but might be different versions.

The simpler solution that does not guard against multiple extensions using the same dependency that might have differing versions is changing return Assembly.LoadFile to return Assembly.LoadFrom here:

• https://github.com/mcmonkeyprojects/SwarmUI/blob/master/src/Core/ExtensionsManager.cs#L184
• https://github.com/mcmonkeyprojects/SwarmUI/blob/master/src/Core/ExtensionsManager.cs#L198

Full disclosure as mentioned in Discord but important to note: This PR was created using Claude because C# build and dependency management confuses the heck out of me. I know the two proposed solutions work because I have a full test suite for my extensions, SwarmUI builds, and my extension with its private dependency works great.

[mcmonkey4eva]

Why is this a retained dict on its own? It doesn't look like there's any reuse, just a single grab on load

[jtreminio]

Fair critique. I've reduced this further.