Rename scala.implicits.Not to scala.util.Not

Having a package just for this type seems weird, especially since we no
longer call them "implicits". After discussion it was deemed not useful
enough to go in the root scala package, so `scala.util` it is.

Author: smarter

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -738,7 +738,7 @@ class Definitions {
     @tu lazy val TypeBox_CAP: TypeSymbol = TypeBoxClass.requiredType(tpnme.CAP)
 
   @tu lazy val MatchCaseClass: ClassSymbol = requiredClass("scala.internal.MatchCase")
-  @tu lazy val NotClass: ClassSymbol = requiredClass("scala.implicits.Not")
+  @tu lazy val NotClass: ClassSymbol = requiredClass("scala.util.Not")
     @tu lazy val Not_value: Symbol = NotClass.companionModule.requiredMethod(nme.value)
 
   @tu lazy val ValueOfClass: ClassSymbol = requiredClass("scala.ValueOf")

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -1234,7 +1234,7 @@ trait Implicits:
              |According to the new implicit resolution rules this is no longer possible;
              |the search will fail with a global ambiguity error instead.
              |
-             |Consider using the scala.implicits.Not class to implement similar functionality.""",
+             |Consider using the scala.util.Not class to implement similar functionality.""",
              ctx.source.atSpan(span))
 
       /** A relation that influences the order in which implicits are tried.

docs/docs/reference/changed-features/implicit-resolution.md

@@ -107,7 +107,7 @@ which means that the alternative `c` would be chosen as solution!
 Scala 2's somewhat puzzling behavior with respect to ambiguity has been exploited to implement
 the analogue of a "negated" search in implicit resolution, where a query `Q1` fails if some
 other query `Q2` succeeds and `Q1` succeeds if `Q2` fails. With the new cleaned up behavior
-these techniques no longer work. But there is now a new special type `scala.implicits.Not`
+these techniques no longer work. But there is now a new special type `scala.util.Not`
 which implements negation directly. For any query type `Q`: `Not[Q]` succeeds if and only if
 the implicit search for `Q` fails.
 

library/src-bootstrapped/scala/implicits/package.scala

@@ -0,0 +1,6 @@
+package scala
+
+package object implicits {
+  @deprecated("scala.implicits.Not has been renamed scala.util.Not", "0.27.0")
+  type Not[A] = scala.util.Not[A]
+}

library/src/scala/implicits/Not.scala renamed to library/src-bootstrapped/scala/util/Not.scala

@@ -1,4 +1,4 @@
-package scala.implicits
+package scala.util
 
 /** A special class used to implement negation in implicit search.
  *