PrmPkg: Changes for edk2 repo transition

Updates the Readme.md files to remove information that was specific
to the package in edk2-staging and adds key definitions being added
for PRM support in the ACPI Specification.

Adds PrmPkg/PrmPkg.ci.yaml to support CI.

Adds PrmPkg to .pytool/CISettings.py.

Adds PrmPkg maintainers to Maintainers.txt.

Cc: Andrew Fish <afish@apple.com>
Cc: Kang Gao <kang.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Benjamin You <benjamin.you@intel.com>
Cc: Liu Yun <yun.y.liu@intel.com>
Cc: Ankit Sinha <ankit.sinha@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Acked-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Liming Gao <gaoliming@byosoft.com.cn>
Acked-by: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Ankit Sinha <ankit.sinha@intel.com>

.pytool/CISettings.py

@@ -65,6 +65,7 @@ class Settings(CiBuildSettingsManager, UpdateSettingsManager, SetupSettingsManag
                 "StandaloneMmPkg",
                 "FatPkg",
                 "CryptoPkg",
+                "PrmPkg",
                 "UnitTestFrameworkPkg",
                 "OvmfPkg",
                 "RedfishPkg",