* build: consolidate Envoy version management
Simplify Envoy version management by consolidating all runtime, build,
and CI sources of Envoy versions into a single plaintext file.
The goal of this change is to avoid common mistakes missing an update of
some Envoy versions (both in general and due to release branch
inconsistency), and enable automated Envoy version updates in the
future.
* ci: add missing ref argument for get-go-version
Supports nightly tests.
Several of our nightly cron jobs are actually running repeatedly
back-to-back during the designated hour. Change the cron to run them
once as intended.
ci: Set Go version consistently via .go-version
Ensure Go version is determined consistently for CI and Docker builds
rather than spread across several different files.
The intent is to eventually replace this with use of the `toolchain`
directive in Go 1.21.
Due to the unintuitive behavior of GHA w.r.t. implicit status check
`success()`, test results were only being uploaded on success (failures
presumably came from retried tests that passed).