Show index type as text rather than numeric ID

[ribiza]

When creating or showing an index, the output for the Kind field is a numeric ID of the type. As we did for collection fields, it's a nice UX improvement to display the corresponding string value there.

stef@carbonino:~$ defradb client collection add '
type Book11 {
  title: String
  plot: String @index(kind:ordered)
  about_v: [Float32!] @index(vector: {dimensions: 3, hnsw: {metric: COSINE}})  @embedding(
    fields: ["title", "plot"], 
    provider: "ollama", 
    model: "embeddinggemma"
  )
}
'
[
  {
    "Name": "Book11",
...
    "Indexes": [
      {
        "Name": "Book11_plot_ASC",
        "ID": 1,
        "Fields": [
          {
            "Name": "plot",
            "Descending": false
          }
        ],
        "Kind": 0,
        "KindDescription": {
          "Unique": false
        },
        "Unique": false
      },
      {
        "Name": "Book11_about_v_ASC",
        "ID": 2,
        "Fields": [
          {
            "Name": "about_v",
            "Descending": false
          }
        ],
        "Kind": 1,
        "KindDescription": {
          "Algorithm": "HNSW",
          "Metric": "COSINE",
          "Dimensions": 3,
          "HNSW": {
            "M": 16,
            "EfConstruction": 128,
            "EfSearch": 64
          }
        },
        "Unique": false
      }
    ],