The WL provides the resource group functionality. It meets the
    following functionality requirements:
    1. It provides functionality to create, drop and alter resource groups.
       The resource group associate a set of controllers which can be applied to
       resources of the system. This is to manage and throttle the resource usage
       consumption for different workloads. In the current WL, resource groups
       contain specification of CPU affinity and thread priority which can be
       applied to threads (which are representatives of workloads).

    2. Resource groups have the attributes name, type (SYSTEM or USER), resource
       group state (enabled or disabled), CPU ID list and thread priority. Resource
       groups can be managed by CREATE RESOURCE GROUP, ALTER RESOURCE GROUP and
       DROP RESOURCE GROUP statements.

    3. Resource group can be associated with a thread, a session and a group of
       threads. We can provide a hint to run a particular query using a resource
       group. The SET RESOURCE GROUP and the hint specification allow to do it.

    4. Every thread in the system by default is associated with USR_default or
       SYS_default resource groups. These resource groups by default allow a
       thread to be run on all CPUS and have the normal (0) thread priority
       of the system.

    5. There is a FORCE option associated with ALTER and DROP RESOURCE GROUP
       statements. It has the following semantics:
       (i). FORCE allows a resource group to be disabled even when some threads
            are using the resource group. It moves the threads (of that
            resource group) into their respective default resource groups.
       (ii). FORCE allows a resource group to be dropped while some threads are
             associated with the resource group. The threads of this resource group
             are moved to respective default resource groups.

        Without FORCE, if some threads are using the resource group, then an error
        ER_RESOURCE_GROUP_BUSY shall be returned.

    6. RESOURCE_GROUP_ADMIN privilege is required for CREATE, DROP and ALTER RESOURCE
       GROUP operation. In addition, this privilege allows assignment of system
       and user resource groups to system & user thread respectively.
       RESOURCE_GROUP_USER privilege is required to assign user resource groups with
       user threads.

    7. Resource group feature is not supported on MacOS and the error ER_FEATURE_UNSUPPORTED
       shall be returned on this platform if user attempts to use the resource group related
       actions. Thread priority is unsupported on FreeBSD and Solaris. In linux, the mysqld
       executable need to have CAP_SYS_NICE capability (to have thread priority tuning available).
       On this platform, if user attempts to set/tune the thread priority, a warning
       indicating the attribute shall be raised.

    8. Performance schema table threads is augmented with a RESOURCE_GROUP column
       and this functionality is provided by the WL#8881.

    9. The resource groups are persisted in the the data dictionary mysql.resource_groups and
       shall be available across reboots and future upgrades.
       The INFORMATION_SCHEMA.RESOURCE_GROUPS view shall expose the resource groups
       defined.
    A common function to validate UTF8 string is provided and this function is used
    from other subsystems in addition to it's use in resource group.