Add ability to disable performance-sensitive relaxed atomic operations at compile time

Adds a `RelaxedAtomic`  wrapper around either `T` or `std::atomic<T>` and `USE_SLOPPY_ATOMICS` preprocessor define. The intent of this flag is to allow easy disabling of atomics on WASM, where even relaxed atomics are expensive because all atomics have `seq_cst` semantics.

Passed non regression STC
LLR: 2.99 (-2.94,2.94) <-1.75,0.25>
Total: 50624 W: 12976 L: 12776 D: 24872
Ptnml(0-2): 112, 5445, 14005, 5631, 119
https://tests.stockfishchess.org/tests/view/6a1f690e818cacc1db0ad2c7

Passed non-regression STC SMP
 LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 163696 W: 41514 L: 41438 D: 80744
Ptnml(0-2): 162, 18272, 44904, 18348, 162
https://tests.stockfishchess.org/tests/view/6a21fb97351b79f679cc44b3

Using this class for the TT also allows us to remove the TSAN suppressions, since the UB is fixed.

closes https://github.com/official-stockfish/Stockfish/pull/6877

No functional change

tests/testing.py

@@ -43,28 +43,6 @@ class Valgrind:
         return ["valgrind", "--error-exitcode=42", "--fair-sched=try"]
 
 
-class TSAN:
-    @staticmethod
-    def set_tsan_option():
-        with open(f"tsan.supp", "w") as f:
-            f.write(
-                """
-race:Stockfish::TTEntry::read
-race:Stockfish::TTEntry::save
-race:Stockfish::TTWriter::penalize
-race:Stockfish::TranspositionTable::probe
-race:Stockfish::TranspositionTable::hashfull
-"""
-            )
-
-        os.environ["TSAN_OPTIONS"] = "suppressions=./tsan.supp"
-
-    @staticmethod
-    def unset_tsan_option():
-        os.environ.pop("TSAN_OPTIONS", None)
-        os.remove(f"tsan.supp")
-
-
 class EPD:
     @staticmethod
     def create_bench_epd():