server: pin executable pages in memory

In some instances (eg, cockroachlabs/support#3437) we've observed memory-constrained environments inducing page fault thrashing. Frequent page faults slow execution to a crawl and keep disks busy reading and re-reading the Cockroach binary over and over. These frequent page faults can slow execution so significantly that it becomes counterproductive for the process to even remain running. We'd prefer the process to be OOM killed in such a state.

We should consider approaches to pinning the Cockroach binary's pages into the page cache to ensure that we never page fault thrash on the executable itself.

Jira issue: CRDB-54942