v4.4.1 - Performance improvements, versioned docker tags

The main feature of this release is significant performance improvements — enjoy!

We also overhauled how Docker builds work, so they're now tagged in a more sensible manner. Almost all previous tags have been deleted. From now onwards we have versioned Docker images:

• graphile/postgraphile:4 will give you the latest stable in the "v4.x.x" line (no alphas, betas, rcs); this is the recommended version to use
• Every new vX.Y.Z git tag (i.e. no alpha/beta/rc) will automatically release graphile/postgraphile:X-Y and graphile/postgraphile:X-Y-Z
• graphile/postgraphile:latest will give you the latest stable (but beware of major version bumps!)
• graphile/postgraphile:next will give you the equivalent of what's on master right now (i.e. pre-release/bleeding edge/nightly)

We're currently in a teething period for this, so there may be some bumpiness - if you face any issues, please let me know via GitHub issues or discord.

NOTE: this only applies to future releases; we are not back-filling previous releases, so there's not many tags to choose from right now.

Other changes:

• update various dependencies
• significant performance improvements
• fix a bug with standalone LDS server announcements for insert/update (thanks @pepijnverburg)
• export more TypeScript interfaces from graphile-utils
• add missing dependencies (thanks @michaelbeaumont)
• respect externalUrlBase for websockets (thanks @DvdGiessen)
• typo fixes (thanks @angelosarto, @ludwigbacklund)
• add support for PGHOSTADDR envvar if PGHOST is not present (thanks @encima)
• 🚨 Remove invalid fields from payloads for SETOF function mutations (these fields were never valid, so any client using them would already be broken, thus I am not classing this as a breaking change).