Fix issue with static this references erroring in quoted code

[jchyb]

Previously, inherited methods, even if accessed via static objects, were not able to be used in quotations, unless explicitly pointed to with a non-this prefix. This was due to the fact that during the cross-stage safety check, first the method itself was checked for if it was static (which for the inherited method, it was not), and if not, the prefix was checked further, erroring on any this tree found along the way.

This was fixed by allowing this trees if they point to static objects. This way not only is the initial issue fixed, but also we are able to freely reference static methods with this, like '{this.objectMethod} (whereas previously, only '{Object.objectMethod} or '{objectMethod} were allowed, despite them all pointing to the same static method).

Fixes #22592

[hamzaremmal]

I've pushed a bit the tests locally and everything behaves as expected:

import scala.quoted.*

trait Foo:
  def inherited = ()
  def inheritedArg(arg: Any) = ()

type HideBar = Bar
class Bar extends Foo:
  def local = ()
  def localArg(arg: Any) = ()

  val self: HideBar = this

  def macro01(using Quotes): Expr[Unit] = '{ local }
  def macro02(using Quotes): Expr[Unit] = '{ inherited }
  //def macro03(using Quotes): Expr[Unit] = '{ Bar.local }
  //def macro04(using Quotes): Expr[Unit] = '{ Bar.inherited }
  def macro05(using Quotes): Expr[Unit] = '{ this.local }
  def macro06(using Quotes): Expr[Unit] = '{ this.inherited }
  def macro07(using Quotes): Expr[Unit] = '{ self.local }
  def macro08(using Quotes): Expr[Unit] = '{ self.inherited }
  def macro09(using Quotes): Expr[Unit] = '{ localArg(this) }
  def macro10(using Quotes): Expr[Unit] = '{ inheritedArg(this) }
  //def macro11(using Quotes): Expr[Unit] = '{ Bar.localArg(this) }
  //def macro12(using Quotes): Expr[Unit] = '{ Bar.inheritedArg(this) }
  def macro13(using Quotes): Expr[Unit] = '{ this.localArg(this) }
  def macro14(using Quotes): Expr[Unit] = '{ this.inheritedArg(this) }
  def macro15(using Quotes): Expr[Unit] = '{ self.localArg(this) }
  def macro16(using Quotes): Expr[Unit] = '{ self.inheritedArg(this) }

and

import scala.quoted.*

trait Foo:
  def inherited = ()
  def inheritedArg(arg: Any) = ()

type HideBar = Bar.type
object Bar extends Foo:
  def local = ()
  def localArg(arg: Any) = ()

  val self: HideBar = this

  def macro01(using Quotes): Expr[Unit] = '{ local }
  def macro02(using Quotes): Expr[Unit] = '{ inherited }
  def macro03(using Quotes): Expr[Unit] = '{ Bar.local }
  def macro04(using Quotes): Expr[Unit] = '{ Bar.inherited }
  def macro05(using Quotes): Expr[Unit] = '{ this.local }
  def macro06(using Quotes): Expr[Unit] = '{ this.inherited }
  def macro07(using Quotes): Expr[Unit] = '{ self.local }
  def macro08(using Quotes): Expr[Unit] = '{ self.inherited }
  def macro09(using Quotes): Expr[Unit] = '{ localArg(this) }
  def macro10(using Quotes): Expr[Unit] = '{ inheritedArg(this) }
  def macro11(using Quotes): Expr[Unit] = '{ Bar.localArg(this) }
  def macro12(using Quotes): Expr[Unit] = '{ Bar.inheritedArg(this) }
  def macro13(using Quotes): Expr[Unit] = '{ this.localArg(this) }
  def macro14(using Quotes): Expr[Unit] = '{ this.inheritedArg(this) }
  def macro15(using Quotes): Expr[Unit] = '{ self.localArg(this) }
  def macro16(using Quotes): Expr[Unit] = '{ self.inheritedArg(this) }

[jchyb]

Thank you @hamzaremmal! It was a good idea to test those additional cases, especially the HideBar ones (I hadn't thought of that case).