RFR: Fix Zero builds

[Aleksey Shipilev]

Current Zero builds (including ones in GHA) fail like this:


In file included from /Users/shipilev/Work/shipilev-shenandoah/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp:28:
In file included from /Users/shipilev/Work/shipilev-shenandoah/src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.hpp:30:
/Users/shipilev/Work/shipilev-shenandoah/src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp:452:17: error: inline function 'ShenandoahHeap::get_young_evac_reserve' is not defined [-Werror,-Wundefined-inline]
  inline size_t get_young_evac_reserve() const;
                ^
/Users/shipilev/Work/shipilev-shenandoah/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp:110:50: note: used here
      size_t max_young_cset    = (size_t) (heap->get_young_evac_reserve() / ShenandoahEvacWaste);


This is because with Zero, we don't have the transitive include to `shenandoahHeap.inline.hpp`, yet `shenandoahAdaptiveHeuristics.cpp` uses it. The fix is -- as usual -- to add the explicit include.

Additional testing:
  - [x] macosx-aarch64-zero-fastdebug
  - [ ] GHA

-------------

Commit messages:
 - Fix

Changes: https://git.openjdk.org/shenandoah/pull/244/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=244&range=00
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/shenandoah/pull/244.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/244/head:pull/244

PR: https://git.openjdk.org/shenandoah/pull/244