runtime: retype mheap.pagesSwept as atomic.Uint64

runtime: retype mheap.pagesSwept as atomic.Uint64

[git-generate]
cd src/runtime
mv export_test.go export.go
GOROOT=$(dirname $(dirname $PWD)) rf '
  add mheap.pagesSwept pagesSwept_ atomic.Uint64 // pages swept this cycle
  ex {
    import "runtime/internal/atomic"

    var t mheap
    var v, w uint64
    var d int64

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

Change-Id: Ife99893d90a339655f604bc3a64ee3decec645ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/356709
Trust: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Austin Clements <austin@google.com>