Previously, vmagent produced parsing error for 'multitenant' auth token
value for the cases:
* data ingestion with enableMultitentEndpoints
* data scrapping at promscrape
It's inconsistent to the other VictoriaMetrics components.
Since 'multitenant' is well-known token value for multitenancy via
labels. And vmagent is intended to be compatible with vminsert ingestion
endpoints.
This commit replaces NewToken with NewTokenPossibleMultitenant function
for token parsing. It allows to use multitenant value for it. And it
makes token values consistent for the all components.
Related issue:
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7694
430163d01a
