runtime: retype mheap.pagesSweptBasis as atomic.Uint64

runtime: retype mheap.pagesSweptBasis as atomic.Uint64

[git-generate]
cd src/runtime
mv export_test.go export.go
GOROOT=$(dirname $(dirname $PWD)) rf '
  add mheap.pagesSweptBasis pagesSweptBasis_ atomic.Uint64 // pagesSwept to use as the origin of the sweep ratio
  ex {
    import "runtime/internal/atomic"

    var t mheap
    var v, w uint64
    var d int64

    t.pagesSweptBasis -> t.pagesSweptBasis_.Load()
    t.pagesSweptBasis = v -> t.pagesSweptBasis_.Store(v)
    atomic.Load64(&t.pagesSweptBasis) -> t.pagesSweptBasis_.Load()
    atomic.LoadAcq64(&t.pagesSweptBasis) -> t.pagesSweptBasis_.LoadAcquire()
    atomic.Store64(&t.pagesSweptBasis, v) -> t.pagesSweptBasis_.Store(v)
    atomic.StoreRel64(&t.pagesSweptBasis, v) -> t.pagesSweptBasis_.StoreRelease(v)
    atomic.Cas64(&t.pagesSweptBasis, v, w) -> t.pagesSweptBasis_.CompareAndSwap(v, w)
    atomic.Xchg64(&t.pagesSweptBasis, v) -> t.pagesSweptBasis_.Swap(v)
    atomic.Xadd64(&t.pagesSweptBasis, d) -> t.pagesSweptBasis_.Add(d)
  }
  rm mheap.pagesSweptBasis
  mv mheap.pagesSweptBasis_ mheap.pagesSweptBasis
'
mv export.go export_test.go

Change-Id: Id9438184b9bd06d96894c02376385bad45dee154
Reviewed-on: https://go-review.googlesource.com/c/go/+/356710
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Knyszek <mknyszek@google.com>