* 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.
Michael Zalimeni