Stringify an `AttributeValue` for assertion purposes.

When you complete stack switch, you need to call this method. `shadow_stack` should be the one given to you when you call `StartSwitchFiber`, i.e., *

Allocate a memory block of size `FLAGS_flare_fiber_stack_size`. The result points to the top of the stack (lowest address).

Deregister a going-to-be-freed stack. `ptr` points to stack bottom.

These methods are used frequently, so we make them inline-able here.

`stack` should point to the top of the stack.

Accessor.

Not very performant but we don't expect `Key`s` to be access too often.

@sa: RpcChannel::GetBinlogCorrelationId.

Returns the event loop we're associated with.

Same as `TryGetFactory` except that this method aborts if the requested class is not found.

Non-conformant: Case sensitive. Won't hurt for UT, though.

`Random()` does not perform quite well, besides, we don't need a "real" random number for NSLB either, so we use a thread-local RR ID for default NSLB

Get timeout in relative (to `last_reset_`) time.

Get top (highest address) of the runtime stack (after skipping this control structure). Calling this method on main fiber is undefined.

This registry is filled by `RegisterCallback()`.