test: use ci job matrix and fix acceptance tests

[jooola]

• Refactor the Github workflow and use a job matrix
• Split unit tests and acceptance tests
• Do not skip acceptance test when they are run
• Print acceptance test log files, this ensures we always see the logs even in the CI, with no additional code.
• Setup tps-action to provide a HCLOUD_TOKEN
• Ensure packer-plugin-hcloud binary has a .exe on windows acceptance tests, or the binary will be ignored
• Use the working directory as packer plugin path, this bypass the additional logic of setting up a new directory ~/.config/packer/plugins directory, which increases complexity in a cross-platform context. Note that ~ is not always expanded in the Windows CI jobs, it depends on the context where the tilde is executed.
• Ensure we always use the bash shell in the cross-platform CI jobs.