drenv addons: Use latest release for all tools for tools installed from github release

[nirs]

Example from kubectl-gather:

tag="$(curl -fsSL https://api.github.com/repos/nirs/kubectl-gather/releases/latest | jq -r .tag_name)"
os="$(uname | tr '[:upper:]' '[:lower:]')"
machine="$(uname -m)"
if [ "$machine" = "aarch64" ]; then machine="arm64"; fi
if [ "$machine" = "x86_64" ]; then machine="amd64"; fi
curl -L -o kubectl-gather https://github.com/nirs/kubectl-gather/releases/download/$tag/kubectl-gather-$tag-$os-$machine
sudo install kubectl-gather /usr/local/bin
rm kubectl-gather

With this we don't need to change the instructions again, except for "tested with version x.y.z" note.

If we have to use specific version we can make tag constant.