[2.15] Use a sha-pinned version of setup-envtest

[ericpromislow]

Ref #1899

[tomleb]

To keep consistency with the other repository (steve), what do you think of using this script to install setup-envtest? https://github.com/rancher/steve/blob/main/scripts/install-envtest.sh

The script also checksums the binaries (apiserver / etcd) that are being installed by setup-envtest.

EDIT: Oops, meant this to be a comment

[crobby]

@ericpromislow Should we try to get this in?

[ericpromislow]

Regarding @tomleb's suggestion, I can either run install-envtest in steve and copy/paste the workflow lines from steve into lasso, or I can copy the scripts from lasso into steve and run them there. But then I have to copy steve/gotools/setup-envtest/ as well, and have to keep the SHAs in lasso in sync with steve, and the versions in lasso's go.mod in sync with steve's. Sounds easier to just copy over the workflow command from steve.

[crobby]

Seems like a reasonable approach.

Tom meant the text to be a comment, not a requested change