v1.15.0-cadence-v1.0.0-preview.14

What's Changed

• Update version.txt to v1.15.0 by @chasefleming in #1459
• Use stderr to output test runner logs by @jribbink in #1461
• Switch hardcoded Mainnet contracts check to use system contracts library by @chasefleming in #1466
• add flow package depdendenices into version by @ianthpun in #1467
• Use .zip archives for Windows releases by @jribbink in #1473
• Merge master into feature/stable-cadence by @jribbink in #1475
• validate contract by @ianthpun in #1477
• Update to Cadence v1.0.0-preview.18 by @SupunS in #1480

Full Changelog: v1.15.0-cadence-v1.0.0-preview.13...v1.15.0-cadence-v1.0.0-preview.14