Add Swap utilization detector

[jmapro]

No description provided.

[JMHAUTBOIS-Claranet]

default value for swap_disabled is null, which means swap detector will be enabled, considering the coalesce function.
All platforms are not the same regarding swap, maybe we should prevent swap alerts to pop-up inadvertently ? (i.e. have default = false ?)

[jmapro]

This detector is called swap, but it is also applicable to windows page file as the splunk agent use the same metric for both OS.

[Poil]

Monitoring swap usage is useless if it's not correlated to memory usage, Kernel will always try to move low priority to Swap.
We should monitors pages in and out of swap space, and system free memory.
Also what to do when you trigger swap is full ? Disable swap and enable it again ?

Good article : https://support.cpanel.net/hc/en-us/articles/360060508193-My-server-is-continuously-using-large-amounts-of-swap-space