Fix handling edits in types nested in reloadable types

[tmat]

Fixes #76989

Allows arbitrary edits within @function block of Razor cshtml page. Previously edits to types defined in this block were applied "in-place" and thus subject to limitations on non-reloadable type edits.

E.g. adding an enum value was reported as rude edit:

@page
...
@function {
   enum E
   {
     A,
     B,
     // C 
   } 
}

[tmat]

@DustinCampbell ptal

[DustinCampbell]

Love it! 💘

cc @davidwengier as FYI about the improvement to Razor ENC.