removes contentious usage of mutexes in LRU, which
were never really reused in any manner; we do not
need it.
To trust hosts, the correct way is TLS certs; this PR completely
removes this dependency, which has never been useful.
```
0 0% 100% 25.83s 26.76% github.com/hashicorp/golang-lru/v2/expirable.(*LRU[...])
0 0% 100% 28.03s 29.04% github.com/hashicorp/golang-lru/v2/expirable.(*LRU[...])
```
Bonus: use `x-minio-time` as a nanosecond to avoid unnecessary
parsing logic of time strings instead of using a more
straightforward mechanism.
8e618d45fc