Replace bindata packages with stdlib go:embed.
Modernize some uiserver code with newer interfaces introduced in go 1.16 (mainly working with fs.File instead of http.File.
Remove steps that are no longer used from our build files.
Add Github Action to detect differences in agent/uiserver/dist and verify that the files are correct (by compiling UI assets and comparing contents).
Adds additional 'enterprise' text underneath the 'startup' logo if the
ui is built with a CONSUL_BINARY_TYPE environment variable that doesn't
equal `oss`.
1. Prints the $version that you are passing through to the docker
container
2. Prints the CONSUL_VERSION that is used in the UI v2 footer
3. Additionally added a `mkdir -p` so so `make ui-docker` runs with a
clean exit if run in isolation
