ci: Combine linux and darwin tag pipelines

[camscale]

Combine the pipelines for tag builds of linux and darwin builds of the
terraform provider and event-handler. These are pure Go programs so can
easily be cross-compiled using GOOS/GOARCH. The "tricky" part is the
universal binary, solved by using https://github.com/konoui/lipo - a Go
version of lipo (the tool that constructs universal binaries) that can
run on Linux.

This removes Apple Mac machines from the release pipeline of the
plugins.

[wadells]

Would you link your testing? I think that is the most important merge criteria.

[camscale]

terraform: https://drone.platform.teleport.sh/gravitational/teleport-plugins/3014
event-handler: https://drone.platform.teleport.sh/gravitational/teleport-plugins/3013

[camscale]

I have downloaded these builds from the S3 bucket and run them on my Mac (arm64). I needed to first remove the quarantine bit (xattr -d com.apple.quarantine <binary>) from the downloaded binaries, and they both execute fine and produced a help message (event-handler) or the "this is a plugin" message (terraform provider).

[camscale]

I have also downloaded the linux versions and tested them in the same way - executing the binaries to ensure they can run. All good, same results:

> ./terraform-provider-teleport
This binary is a plugin. These are not meant to be executed directly.
Please execute the program that consumes these plugins, which will
load any plugins automatically

> ./teleport-event-handler version
Teleport event handler v14.0.0-camh.1 go1.21.1