sanitizer_common: revert StaticSpinMutex ctor

Patch "sanitizer_common: modernize SpinMutex" added default
ctor to StaticSpinMutex. But it broke some gcc bots with:

scudo_tsd_exclusive.cpp:25:22: error: non-local variable
‘__scudo::TSD’ declared ‘__thread’ needs dynamic initialization

https://lab.llvm.org/buildbot/#/builders/105/builds/12649

Unfortunatly none of empty ctor {}, no ctor, default constexpr ctor
work for different reasons. So remove StaticSpinMutex ctor
entirely and move deleted copy ctor back to SpinMutex.

Differential Revision: https://reviews.llvm.org/D106424