Syntax support for configuring distance-metric within the field

[jobergum]

Today distance-metric is configured within the attribute block which also controls things like paged, fast-search etc.

field embedding type tensor<float>(v[1024]) {
     indexing: input text | embed mxbai | attribute | index
     attribute {
        distance-metric:prenormalized-angular
     }
  }

I think we should allow configuring distance-metric within the tensor field

field embedding type tensor<float>(v[1024]) {
     indexing: input text | embed mxbai | attribute | index
     distance-metric:prenormalized-angular
}

Just because it looks prettier and it's not straight forward to explain why it is tied to attribute