bazel: use prebuilt Go toolchain (go.dev/dl)

We had to switch to a Go toolchain from nixpkgs,
since prebuilt Go toolchain versions were not usable on NixOS.
Since Go 1.21, the prebuilt Go toolchain is statically linked
and works out of the box.

Reference: golang/go#57007

WORKSPACE.bazel

@@ -131,16 +131,11 @@ load("//bazel/toolchains:go_module_deps.bzl", "go_dependencies")
 # gazelle:repository_macro bazel/toolchains/go_module_deps.bzl%go_dependencies
 go_dependencies()
 
-load("@io_bazel_rules_go//go:deps.bzl", "go_rules_dependencies")
+load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
 
 go_rules_dependencies()
 
-load("@io_tweag_rules_nixpkgs//nixpkgs:toolchains/go.bzl", "nixpkgs_go_configure")
-
-nixpkgs_go_configure(
-    nix_file = "//bazel/go:go.nix",
-    repository = "@nixpkgs",
-)
+go_register_toolchains(version = "1.21.5")
 
 load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")
 

dev-docs/workflows/bump-go-version.md

@@ -3,15 +3,8 @@
 
 ## Steps
 
-1. Replace "1.xx.x" with the new version (see [example](https://github.com/edgelesssys/constellation/commit/9e1a0c06bfda0171958f0776633a9a53f521144d))
-2. Update the nix hash
+Replace "1.xx.x" with the new version in [WORKSPACE.bazel](/WORKSPACE.bazel):
 
-    Once updated run `bazel run //:tidy` and you will see a failure such as:
-
-    ```
-        > error: hash mismatch in fixed-output derivation '/nix/store/r85bdj6vrim7m5vlybdmzgca7d0kcb4n-go1.21.4.src.tar.gz.drv':
-      >          specified: sha256-GG8rb4yLcE5paCGwmrIEGlwe4T3LwxVqE63PdZMe5Ig=
-      >             got:    sha256-R7Jqg9K2WjwcG8rOJztpvuSaentRaKdgTe09JqN714c=
-    ```
-    Simple replace the hash with the got value.
-3. Ask @katexochen to build the thing and push it into his cache.
+```starlark
+go_register_toolchains(version = "1.xx.x")
+```