* prometheus labels incl tests
* enable label in main, add log, docs
* revert the option to query by label
* revert the option to query by label
* PromClient instantiate by func,white space removal
* revert whitespace fix for readability.
* revert removal of newlines for readability
* rename New to NewPromClient to improve readability
Co-authored-by: simp <simp@saxobank.com>