Revert "VectorBuilder avoids copying data if possible"

[szeiger]

This reverts commit 18224fd.

Reverts #7588 which caused
scala/bug#11636.

See #8246 for context.

[joshlemer]

Should we add to VectorTest.scala?

  @Test
  def i11636(): Unit = {

    val a: Vector[String] = "O" +: Iterator.continually("E").take(2101).foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val a0: ArraySeq[String] = ArraySeq("O") ++ Iterator.continually("E").take(2101) ++ ArraySeq("C")

    val b: Vector[String] = "O" +: Iterator.continually("E").take(223) .foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val b0: ArraySeq[String] = ArraySeq("O") ++ Iterator.continually("E").take(223) ++ ArraySeq("C")

    val c: Vector[String] = "O" +: Iterator.continually("E").take(135) .foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val c0: ArraySeq[String] = ArraySeq("O") ++ Iterator.continually("E").take(135) ++ ArraySeq("C")

    val d: Vector[String] = "O" +: Iterator.continually("E").take(0)   .foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val d0: ArraySeq[String] = ArraySeq("O", "C")

    val e: Vector[String] = "O" +: Iterator.continually("E").take(376) .foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val e0: ArraySeq[String] = ArraySeq("O") ++ Iterator.continually("E").take(376) ++ ArraySeq("C")

    val f: Vector[String] = "O" +: Iterator.continually("E").take(365) .foldLeft(Vector.empty[String])((v, e) => v :+ e) :+ "C"
    val f0: ArraySeq[String] = ArraySeq("O") ++ Iterator.continually("E").take(365) ++ ArraySeq("C")
    
    assertEquals(a0, a)
    assertEquals(b0, b)
    assertEquals(c0, c)
    assertEquals(d0, d)
    assertEquals(e0, e)
    assertEquals(f0, f)

    assertEquals(a0 ++ b0, a ++ b)
    assertEquals(a0 ++ b0 ++ c0, a ++ b ++ c)
    assertEquals(a0 ++ b0 ++ c0 ++ d0, a ++ b ++ c ++ d)
    assertEquals(a0 ++ b0 ++ c0 ++ d0 ++ e0, a ++ b ++ c ++ d ++ e)
    assertEquals(a0 ++ b0 ++ c0 ++ d0 ++ e0 ++ f0, a ++ b ++ c ++ d ++ e ++ f)
  }

[joshlemer]

this line doesn't need to change.

[szeiger]

sigh the MiMa whitelist is really, really annoying. Almost every PR requires new entries which will cause conflicts with every other PR.

[joshlemer]

Thank you @szeiger