all: prepare for formatting any as 'any' in type strings

Make a couple of small changes to support keeping track of the
predeclared any by pointer identity, and formatting it as 'any'. This
should allow x/tools trybots to pass on CL 363974.

Updates golang/go#49583

Change-Id: I79cffee6adbf000a7251dbea4091fdd7b8fdcf0a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/364194
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>

Author: findleyr

go/internal/gcimporter/support_go118.go

@@ -16,5 +16,8 @@ func additionalPredeclared() []types.Type {
 	return []types.Type{
 		// comparable
 		types.Universe.Lookup("comparable").Type(),
+
+		// any
+		types.Universe.Lookup("any").Type(),
 	}
 }

internal/lsp/testdata/godef/infer_generics/inferred.go

@@ -1,6 +1,6 @@
 package inferred
 
-func app[S interface{ ~[]E }, E any](s S, e E) S {
+func app[S interface{ ~[]E }, E interface{}](s S, e E) S {
 	return append(s, e)
 }