5.12 merge window, part 2

While KFENCE was designed to be deployed at scale and for our use-cases are looking at KFENCE_SAMPLE_INTERVAL >= 500 milliseconds, I'm also aware of a KFENCE deployment where they chose KFENCE_SAMPLE_INTERVAL=1 ms (and lower with experimental patches) and very large KFENCE_NUM_OBJECTS (65535 -> 512 MiB) and found bugs that way. For such aggressive configs, see what performance you get, but my guess is that at sample intervals as low as 1 ms, you'll want to switch to KFENCE's non-static-branch mode with CONFIG_KFENCE_STATIC_KEYS=n.