Fix memory leak in Stripe destructor

[bneradt]

Add a destructor to the Stripe class to properly free the directory memory allocated in _init_directory(). The memory was allocated via ats_memalign or ats_alloc_hugepage but never freed when Stripe objects were destroyed. A new private member tracks whether hugepages were used so the destructor can call the appropriate free function. This was discovered via an infrequent ASAN failure in the
cache_disk_replacement_stability regression test, which reported a ~27GB leak from 24 StripeSM objects that went out of scope without releasing their directory buffers.

=================================================================
==5207==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 29272965120 byte(s) in 24 object(s) allocated from:
    #0 0x7f8b9cd1669c in __interceptor_posix_memalign (/lib64/libasan.so.6+0xb569c)
    #1 0xa69d99 in ats_memalign(unsigned long, unsigned long) ../src/tscore/ink_memory.cc:108
    #2 0xfd96e2 in Stripe::_init_directory(unsigned long, int, int) ../src/iocore/cache/Stripe.cc:159
    #3 0xfd905f in Stripe::Stripe(CacheDisk*, long, long, int, int) ../src/iocore/cache/Stripe.cc:97
    #4 0xfdc7ef in StripeSM::StripeSM(CacheDisk*, long, long, int, int) ../src/iocore/cache/StripeSM.cc:120
    #5 0xff8c81 in std::_MakeUniq<StripeSM>::__single_object std::make_unique<StripeSM, CacheDisk*, long, int>(CacheDisk*&&, long&&, int&&) (/tmp/ats-quiche/bin/traffic_server+0xff8c81)
    #6 0xff4797 in RegressionTest_cache_disk_replacement_stability(RegressionTest*, int, int*) ../src/iocore/cache/CacheTest.cc:458
    #7 0xa4c994 in start_test ../src/tscore/Regression.cc:83
    #8 0xa4cd6c in RegressionTest::run(char const*, int) ../src/tscore/Regression.cc:106
    #9 0xa1a2a8 in mainEvent ../src/traffic_server/traffic_server.cc:1570
    #10 0x9fd61a in Continuation::handleEvent(int, void*) ../include/iocore/eventsystem/Continuation.h:228
    #11 0x13373e7 in EThread::process_event(Event*, int, long) ../src/iocore/eventsystem/UnixEThread.cc:171
    #12 0x133809c in EThread::execute_regular() ../src/iocore/eventsystem/UnixEThread.cc:288
    #13 0x1338a7b in EThread::execute() ../src/iocore/eventsystem/UnixEThread.cc:383
    #14 0x13356e8 in spawn_thread_internal ../src/iocore/eventsystem/Thread.cc:75
    #15 0x7f8b9abeb1c9 in start_thread (/lib64/libpthread.so.0+0x81c9)

[bneradt]

@zwoop has a fix for this contained inside of #12717 (which may be broken out as a separate PR later). I'll close this PR, which has it's own problems at anyrate, judging from the failed CI runs.