Make {.requiresInit.} to work for distinct types (#15869)

Make `requiresInit` pragma to work for distinct types in addition to
objects. Tagging of distinct types with `requiresInit` pragma was
already supported, but its impact wasn't applied. Now its behavior when
applied on distinct types is as follows.

Given the following distinct type definitions:

  ```nim
  type
    DistinctObject {.requiresInit, borrow: `.`.} = distinct MyObject
    DistinctString {.requiresInit.} = distinct string
  ```

The following code blocks will fail to compile:

  ```nim
  var foo: DistinctFoo
  foo.x = "test"
  doAssert foo.x == "test"
  ```

  ```nim
  var s: DistinctString
  s = "test"
  doAssert s == "test"
  ```

But these ones will compile successfully:

  ```nim
  let foo = DistinctFoo(Foo(x: "test"))
  doAssert foo.x == "test"
  ```

  ```nim
  let s = "test"
  doAssert s == "test"
  ```

compiler/typeallowed.nim

@@ -260,4 +260,5 @@ proc directViewType*(t: PType): ViewTypeKind =
     result = noView
 
 proc requiresInit*(t: PType): bool =
-  (t.flags * {tfRequiresInit, tfNotNil} != {}) or classifyViewType(t) != noView
+  (t.flags * {tfRequiresInit, tfNeedsFullInit, tfNotNil} != {}) or
+  classifyViewType(t) != noView