Resolve imported class constant fetches

[jbuncle]

Summary

• resolve imported class aliases in class constant fetch values for class constants and namespace constants
• keep self, parent, and already-fully-qualified class constant fetches intact while resolving imported aliases semantically
• add characterization coverage showing alias-target changes affect semantic version diffing

Validation

• udocker run -v /data/data/com.termux/files/home/projects/jbuncle/php-autosemver:/app -w /app composer2 sh -lc "find src bin tests -type f -name '*.php' -print0 | xargs -0 -n1 php -l && COVERAGE_MIN=90 COVERAGE_JSON=/tmp/coverage.json COVERAGE_SUMMARY=/tmp/coverage-summary.md phpdbg -qrr tests/coverage.php"
• coverage: 91.72% (908/990)