The config schema map was using string_view keys that pointed to the name field of Option objects stored in the global ceph_options vector. When the vector is destroyed during program exit, the Option objects are freed, but background threads (like BlueStore::MempoolThread) may still be accessing config options, causing use-after-free.

ASan reported:
  READ of size 19 at 0x503000047c80 thread T411
    #12 md_config_t::find_option(std::string_view) const config.cc:261
    #17 BlueStore::MempoolThread::entry() BlueStore.cc:5591

  0x503000047c80 is located 0 bytes inside of 20-byte region
  freed by thread T0 here:
    #7 Option::~Option() options.h:15
    #13 std::vector<Option>::~vector() stl_vector.h:730
    #14 __run_exit_handlers stdlib/exit.c:113

  previously allocated by thread T0 here:
    #7 Option::Option(Option const&) options.h:15
    #18 build_options() build_options.cc:44

Fix by converting ceph_options from a global variable to a function get_ceph_options() that returns a reference to a static pointer that is never destroyed. This ensures the Option objects remain valid for the lifetime of the program, even during exit when background threads may still be accessing them.

This preserves the memory efficiency of using string_view keys in the schema map while fixing the lifetime issue.

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