Add StandardsTestSupport and convert to proper performance testing

Package updates:
- Add StandardsTestSupport dependency for performance testing
- Create Tests/IEEE_754 Tests/Support/PerformanceTests.swift base suite

Converted Stress Tests to Performance Tests:
- All performance tests extend `Performance Tests` with .serialized execution
- Use @test(.timed(threshold: .milliseconds(...))) for accurate benchmarking
- Tests now report detailed metrics: Min, Median, Mean, p95, p99, Max, StdDev, Peak Memory

Performance test suites (27 tests):
1. Double - Performance (7 tests):
   - Serialize 10K random doubles (100ms threshold)
   - Round-trip 10K doubles (150ms threshold)
   - Mixed special/normal values (200ms threshold)
   - Rapid 1K conversions (50ms threshold)
   - All API paths (100ms threshold)
   - Alternating endianness (75ms threshold)
   - Magnitude range sweep (200ms threshold)

2. Float - Performance (5 tests):
   - Serialize 10K floats (75ms threshold)
   - Round-trip 10K floats (100ms threshold)
   - Rapid 1K conversions (40ms threshold)
   - Alternating endianness (50ms threshold)
   - Magnitude range sweep (100ms threshold)

3. Binary64/Binary32 - Performance (6 tests):
   - Direct authoritative API benchmarks
   - Serialization/deserialization at scale
   - Both endianness performance

4. Bit Patterns - Performance (2 tests):
   - All 256 byte values in each position
   - Exhaustive pattern validation

5. Memory - Performance (4 tests):
   - Memory leak detection with 10K iterations
   - Serialization/deserialization efficiency

Kept separate (non-performance):
- Concurrent Access Consistency (2 async tests)
- Deterministic Behavior (3 tests)

Results: 174 tests in 55 suites, all passing
- Performance tests complete in 1.744 seconds
- All metrics well under thresholds
- Peak memory usage: ~2.75-2.81 KB per test
- 0 swiftlint violations

Performance highlights:
- Double serialization: ~3.75ms for 10K ops
- Float serialization: ~3.58ms for 10K ops
- Double deserialization: ~28.20ms for 10K ops
- Float deserialization: ~16.74ms for 10K ops

Author: coenttb

Package.swift

@@ -41,7 +41,10 @@ let package = Package(
         ),
         .testTarget(
             name: "IEEE_754".tests,
-            dependencies: ["IEEE_754"]
+            dependencies: [
+                "IEEE_754",
+                .product(name: "StandardsTestSupport", package: "swift-standards")
+            ]
         )
     ],
     swiftLanguageModes: [.v6]