feat(uucore): add shared hardware detection module

Add shared CPU hardware capability detection in uucore to prevent
code duplication across utilities. This provides a unified interface
for detecting CPU features (AVX512, AVX2, PCLMUL, SSE2, ASIMD) and
respecting GLIBC_TUNABLES environment variable.

This unblocks PR #9088 (cksum --debug) and PR #9144 (wc --debug) by
providing a common implementation that both utilities can use.

Features:
- CPU feature detection with caching (singleton pattern)
- GLIBC_TUNABLES parsing for hwcaps restrictions
- Cross-platform support (x86/x86_64, aarch64)
- Comprehensive test coverage
- Zero-cost abstractions using std::arch

Implementation details:
- Uses std::arch feature detection (no external deps for detection)
- Adds cfg-if dependency for conditional compilation
- Feature-gated behind "hardware" feature flag
- Android excluded (no CPUID access in sandboxed environment)

Related: #9088, #9144

Author: naoNao89

.vscode/cspell.dictionaries/jargon.wordlist.txt

@@ -188,3 +188,16 @@ nofield
 # * clippy
 uninlined
 nonminimal
+
+# * CPU/hardware features
+ASIMD
+asimd
+hwcaps
+PCLMUL
+pclmul
+PCLMULQDQ
+pclmulqdq
+TUNABLES
+tunables
+VMULL
+vmull