Before this change, `NewStats` stored the context it was created from on the
`StatsInfo`. Stats groups are never freed -- they are only evicted once there are
`--max-stats-groups` of them -- so each one kept its context, and everything reachable
from it, alive for the life of the process. As the rc creates a group per call,
that included the call's filters and their compiled regexps.
The context was only ever used to get `ci.StatsFileNameLength` from the config.
`StatsInfo` already stores that same `*fs.ConfigInfo`, read from the same
context in `NewStats`.
This change fixes the issue by passing the stored ci to `transferMap.String` and
dropping the context from `StatsInfo`.
nielashandNick Craig-Wood
abae66ee1a