RFR: Remove vestigial command line options and removed unused code

[William Kemper]

On Tue, 12 Oct 2021 12:14:44 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> * Removed ShenandoahUseSimpleCardScanning and ShenandoahPromoteTenuredRegions command line options
>> * Removed preprocessor directives FAST_REMEMBERED_SET_SCANNING and CROSSING_OFFSETS_NO_LONGER_NEEDED
>
> src/hotspot/share/gc/shenandoah/shenandoahScanRemembered.hpp line 541:
> 
>> 539:   ShenandoahCardCluster(RememberedSet *rs) {
>> 540:     _rs = rs;
>> 541:     // HEY!  We don't really need object_starts entries for every card entry.  We only need these for
> 
> Consider changing 'HEY!' to 'TODO' or something. IDEs tend to highlight the latter (mine does).

I'll replace these en masse with another pull request.

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PR: https://git.openjdk.java.net/shenandoah/pull/85