fix(C#): added dependency usings based on types present in renderContext

[sakets594]

Description

change - forcing dependency namespace ("System.Collections.Generic") to be added for list and dictionary in cases where common namespace addition(CSharpRenderer.emitUsings) was skipped

Related Issue

https://github.com/glideapps/quicktype/issues/2523

Motivation and Context

https://github.com/glideapps/quicktype/issues/2523

Previous Behaviour / Output

if you run the C# renderer with --features just-types --array-type list then it creates List<T> properties, but doesn't add the required using System.Collections.Generic;. It also happens without the --array-type list if a Dictionary<K,V> is generated as a property.

1. Example with dictionary command: echo '{ "name": "David","keyval":{"1":{"prop1":1},"2":{"prop1":1},"3":{"prop1":3}} }' | script/quicktype -l csharp --features just-types output:

namespace QuickType
{

    public partial class TopLevel
    {
        public string Name { get; set; }
        public Dictionary<string, Keyval> Keyval { get; set; }
    }

    public partial class Keyval
    {
        public long Prop1 { get; set; }
    }
}

2. Example with array as list command: echo '{ "name": "David","arr":[1,2,3] }' | script/quicktype -l csharp --features just-types --array-type list output:

namespace QuickType
{

    public partial class TopLevel
    {
        public string Name { get; set; }
        public List<long> Arr { get; set; }
    }
}

New Behaviour / Output

with new change using System.Collections.Generic gets added inside name space before class definition when required

1. Example with dictionary command: echo '{ "name": "David","keyval":{"1":{"prop1":1},"2":{"prop1":1},"3":{"prop1":3}} }' | script/quicktype -l csharp --features just-types output:

namespace QuickType
{
    using System.Collections.Generic;

    public partial class TopLevel
    {
        public string Name { get; set; }
        public Dictionary<string, Keyval> Keyval { get; set; }
    }

    public partial class Keyval
    {
        public long Prop1 { get; set; }
    }
}

2. Example with array as list command: echo '{ "name": "David","arr":[1,2,3] }' | script/quicktype -l csharp --features just-types --array-type list output:

namespace QuickType
{
    using System.Collections.Generic;

    public partial class TopLevel
    {
        public string Name { get; set; }
        public List<long> Arr { get; set; }
    }
}

How Has This Been Tested?

Manual testing using command line, covered negative and positive cases of examples provided above [EDIT] - tested with both array and dictionary present in json to validate single using System.Collections.Generic;