[2.6] NEXUS-5714: Status resource without perms

Introduced "perms" query parameter on status resource, that is
checked for presence only (hence, without, or with any value
works). If "perms" query parameter is present, the status
resource will emit permission related info, as it behaved
before this change.

Without this query parameter, status resource emits only what
it's original intent was.

Measured (before vs after) response time differences is 300ms vs 150 ms,
payload size differences is 7009 byte vs 1152 byte

Note: tested with OSS. The numbers would just grow with Pro, as
delivered permissions are extended by Pro plugins like staging and
others. In short: the more plugins that introduce new UI perms the
payload would get bigger (and since permission count would grow,
more CPU to "unravel" them from current user).

CI:
https://bamboo.zion.sonatype.com/browse/NXO-OSSF0-1

Related issue:
https://issues.sonatype.org/browse/NEXUS-5714