message: HashMap -> SmallMap in HeapSummary
  Summary: Following diff needs iteration to be deterministic.
diff: @@ -39,6 +39,7 @@ use std::time::Instant;
  use bumpalo::Bump;
  use either::Either;
  use gazebo::prelude::*;
  +use starlark_map::small_map::SmallMap;
  use crate::collections::StarlarkHashValue;
  use crate::values::layout::avalue::starlark_str;
  @@ -114,7 +115,7 @@ pub struct HeapSummary {
  /// For each type, give the (number of entries, size of all entries).
  /// The size may be approximate as it includes information from
  /// the approximate [`memory_size`](StarlarkValue::memory_size) function.
  - pub(crate) summary: HashMap<&'static str, AllocCounts>,
  + pub(crate) summary: SmallMap<&'static str, AllocCounts>,
  }
  impl HeapSummary {
  @@ -427,7 +428,7 @@ impl Arena {
  // For a given type, the AValueHeader isn't always unique
  // (if they get compiled in different translation units),
  // so not just a simple map.
  - let mut summary = HashMap::new();
  + let mut summary = SmallMap::new();
  for (_, (name, counts)) in entries {
  *summary.entry(name).or_insert_with(AllocCounts::default) += counts;
  }
  