fix: resolve all dist-tags (not just latest) to precise versions for caching

resolveVersion() now uses a semver regex to detect precise versions
(e.g. "0.1.8", "1.0.0-beta.1") and passes them through. Any other
input (e.g. "latest", "alpha", "canary") is treated as a dist-tag
and resolved to a precise version via the npm registry.

Author: fengmk2