* vmalert: allow extra GET params in datasource package
ExtraParams will be added as GET params to every HTTP request made by datasource.
The `roundDigits` param, for example, was substituted by corresponding extra param.
* vmalert: add nocache=1 param for replay process
The `nocache=1` param is VictoriaMetrics specific parameter which prevents it
from caching and boundaries aligning for queries. We set it to avoid cache
pollution in `replay` mode and also to avoid unnecessary time range boundaries
alignment.
* vmalert: mention nocache=1 in replay description
* vmalert: fix bug with unused param
Starting from v1.56.0 VM supports `round_digits` which allows to limit
the number of digits after the decimal point in response value. The feature
can be used to reduce entropy of produced by recording rules values
and significantly improve the compression. See more details in link below.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/525
* changes vmalert Querier with per rule querier
it allows to changes some parametrs based on rule setting
for instance - alert type, tenant for cluster version or event endpoint url.
The change adds no new functionality and aims to move flags definitions
to subpackages that are using them. This should improve readability
of the main function.
