ImportType cleanup/consolidation

[lolopinto]

We have different import types which are different and broken:

• ent/internal/schema/node_data.go

  Lines 190 to 194 in 2691971

  	type ImportPath struct {
  	PackagePath string
  	Import string
  	DefaultImport bool
  	}

  (best one)

• ent/internal/enttype/type.go

  Line 119 in ec7354f

  type FileImport struct {

• ent/internal/graphql/generate_ts_code.go

  Line 2469 in c818639

  type fileImport struct {

• and

  ent/internal/kv/pair.go

  Line 9 in b4b5046

  type Import struct {

  (very different
  and probably not changing but flagging nonetheless)