Rework build process for release

[mdeltito]

refactor(build): switch to goreleaser for builds

This introduces goreleaser to the pipeline in order to more easily generate multiple signed builds, and distribute assets to GitHub as a release.

In addition, some tooling changes:

• Reworked the makefile and build process. Everything is now run through a docker build container. Local tasks still exist for use during development.
• Refactored the test pipeline in Jenkins, removing matrix builds. This isn't really necessary since we are distributing pre-built binaries.
• Switched from golint (which is deprecated) to golangci-lint. This is a more robust code analysis tool.

Ref: LOG-9606

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fix(lint): remove dead code and check errors in test

This fixes two new linting issues:

• Removes unused test functions
• Checks returned errors in httptest server handlers

Ref: LOG-9606

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chore(deps): bump terraform-provider-sdk@2.7.0

This resolves an issue where tests were suddenly failing due to a broken transient dependency

Ref: LOG-9606

[mdeltito]

@charlesthomas @darinspivey I haven't been able to figure out a workaround for running a Jenkins build on a tag, I think we'll need to update the config for this repo (at least ephemerally, at first) to get this going. I can create a REL card for a long-term configuration change for repos that need this.

My plan is to get this merged into the feature branch, update the jenkins project, and then tag a pre-release from there e.g. v1.1.0-pre to verify the full process works end-to-end. Note that the current setup in this PR will still only create a draft release, which will require manual publishing to "release". That extra human step is a feature IMO since releases will be automatically pulled by the registry.