This commit reduces the interface to Load() a bit, in preparation for
unexporting NewBuilder and having everything call Load.
The three arguments are reduced to a single argument by moving the other
two into the options struct.
The three return values are reduced to two by moving the RuntimeConfig
and Warnings into a LoadResult struct.
Flags is an overloaded term in this context. It generally is used to
refer to command line flags. This struct, however, is a data object
used as input to the construction.
It happens to be partially populated by command line flags, but
otherwise has very little to do with them.
Renaming this struct should make the actual responsibility of this struct
more obvious, and remove the possibility that it is confused with
command line flags.
This change is in preparation for adding additional fields to
BuilderOpts.
The logic in parsing data files and converting them to data structures
accidentally removed healthchecks with no Name field, even though we
explicitly state in API documentation that is allowed.
We remove the check for "len(results.Checks) == 1" because if the length
of the array is more than 0, we know that it is not a zero value array.
This allows us to register a singular, unnamed check via the CLI.
Fixes#6796
