Missing constructor for Term.Ident

[liufengyun]

In addition to constructors for Term.Select (#5796), we need constructor for Term.Ident as well in implementing Monocle macros (#5941) . Something similar to that in tpd.scala would be ideal:

def Ident(tp: TermRef)(implicit ctx: Context): Ident

However, currently there are both SymRef and TermRef in tasty reflect, which are not subtype of each other. This makes the API fragmented.

Any ideas @nicolasstucki ?

[liufengyun]

Implemented in #5944 based on TermRef.