Functions: Detect default vs. isolated worker runtime based on project references

[maartenba]

See https://youtrack.jetbrains.com/issue/RIDER-72960

When no local.settings.json can be found to determine the default vs. isolated worker runtime, work out the runtime based on package references.

• <PackageReference Include="Microsoft.NET.Sdk.Functions" ....> -> default worker
• <PackageReference Include="Microsoft.Azure.Functions.Worker" ....> -> isolated worker

Related to #294 and https://youtrack.jetbrains.com/issue/RIDER-72960