add release procedure using goreleaser

[itaysk]

This PR is introducing a GoReleaser workflow that build tracee binary and Docker image, and can push them to GitHub/DockerHub.
related to: #69

GoReleaser is a popular tool for Go projects, and we (aqua) use it in our other OSS Go projects, so we wanted to see if we can use it here as well. It works, but there are a couple of points to consider:

1. The binary build needs the EBPFPROGRAM_BASE64 environment variable. I didn't find a way to define this in the goreleaser yaml, so I create it in the makefile, meaning GoReleaser must be called through the makefile which is awkward solution but was the compromise I found.
2. In a previous PR I introduced a Dockerfile that builds binary and then created a final image using it (multistage dockerfile). But if we're using goreleaser, then goreleaser should build the binary (not the docker builder). In order to accommodate both approaches, I created a new dockerfile for goreleaser which is not building the binary.

Essentially this is about supporting 3 partially overlapping tools for build automation: Makefile/Docker/GoReleaser. I tried to find a middleground between them, let me know if you think it's reasonable.

[simar7]

for my own understanding: how does this work?

[itaysk]

I wanted to be extra careful with actually pushing things, so I created the goreleaserFlags make variable that defaults to --skip-publish --snapshot (which assures nothing scary is done), and the command that is run is appending this variable to the goreleaser command (line 24). but if the use defines the publish make variable (it can have any value, 1 is just an example) then the variable goreleaserFlags variable is emptied so nothing is appended to the goreleaser command, and the defaults are to publish.