Server v140_2

• Remove npmStoreMaxSize, storage.cacheMaxSize, and automatic local S3 cache purging. (#1495, #1501)
• Expire installed npm packages after 1 idle hour, keep packages used by active requests and builds, and free idle packages before retrying an install on ENOSPC. (#1501)
• Cache S3 build metadata in {workDir}/meta-cache.db when storage.cacheDir is enabled. (#1498)
• Reduce deploy downtime by moving startup cleanup to the background and removing old npm directories asynchronously. (#1495, #1501)
• Free build slots while waiting for package installs and fix concurrent build queue resumes. (#1495, #1503)
• Honor build timeouts during dependency resolution and storage writes, free timed out build slots immediately, and cache build timeout errors for 10 minutes. (#1497, #1502)
• Serve cached npm resolutions while refreshing metadata in the background, including during registry outages. (#1488, #1503)
• Share concurrent registry lookups, cancel waits with the request, and return uncached HTTP 408 responses when resolution exceeds 30 seconds. (#1489)
• Fix purge rate limiting, authenticated registry cache invalidation, and races when removing installed packages. (#1503)
• Fix dependency JSON imports, legacy scoped package URLs with *, missing GitHub repository responses, and caching of invalid registry responses. (#1503)
• Skip redundant storage lookups when joining a running build. (#1503)
• Allow comments in the server config file. (#1503)
• Respect container CPU limits for default build concurrency and upgrade golang.org/x/net to v0.60.0. (#1486)