Mitosis Flag Burndown

[tommy-u]

Heads up, I worked on the plans for each, but these are robot changes. They aren't thoroughly tested or some kind of final code I'm necessarily trying to land in this form.

I'm sharing this as a draft to discuss how we want to go about burning down our flags by making them the default behavior in the scheduler.

I did these in ascending order of complexity:

• slice shrinking
• dynamic affinity
• rebalancing
• borrowing
• cpu controller disable
• llc awareness

As an afterthought I also removed:

• reject multicpu pinning (now we always allow)
• verbose mode dead code

Misc:

• hardcoded smt_enabled removed
• root_cgid was not set by userspace so I moved it to enum mitosis_constants as ROOT_CGID = 1

Notes:
I think we want to keep --exiting-task-workaround and --use-lockless-peek until we're certain about kernel fixes.

Some of the commits at the end should be moved to separate cleanup branches.