* vmalert: Add recording rules support.
Recording rules support required additional service refactoring since
it wasn't planned to support them from the very beginning. The list
of changes is following:
* new entity RecordingRule was added for writing results of MetricsQL
expressions into remote storage;
* interface Rule now unites both recording and alerting rules;
* configuration parser was moved to separate package and now performs
more strict validation;
* new endpoint for listing all groups and rules in json format was added;
* evaluation interval may be set to every particular group;
* vmalert: uncomment tests
* vmalert: rm outdated TODO
* vmalert: fix typos in README
* feat: add remoteWrite.maxQueueSize to reduce queue full
* rename remote(write|read) flags to remote(Write|Read) for the sake of consistency
Co-authored-by: xiaobeibei <xiaobeibei@bigo.sg>
