Refactor: all: represent millisecond intervals as guint

Intervals were previously represented as a mix of int, long long, and
unsigned long long. Now, guint is used consistently (chosen because we need to
use millisecond values as a guint argument to g_timeout_add()).

Prefer the new millisecond-specific functions instead of crm_parse_int(),
crm_element_value_int(), and crm_xml_add_int().

This breaks public API backward compatibility. The return value of
crm_parse_interval_spec(), and the interval arguments of crm_action_str(),
generate_op_key(), parse_op_key(), resources_action_create(),
services_action_create(), services_action_cancel(), services_action_kick(), and
the lrmd_api_operations_t exec() and cancel() members, now use guint instead of
other types.