[FAB-15267] Refactor ChannelPolicyManagerGetter mock
[FAB-15267] Refactor ChannelPolicyManagerGetter mock

Refactored ChannelPolicyManagerGetter mock in core/committer
/txvalidator/v20 to generate from local interface.

Change-Id: I610e27971ec3eddc2b470729054bf64b7231fc19
Signed-off-by: Chongxin Luo <7c0175c1e9b282afeb442298363614962e031204@ibm.com>

stemlending/fabric,binhn/fabric,manish-sethi/fabric-sidedb,hyperledger/fabric,manish-sethi/fabric-sidedb,muralisrini/fabric,binhn/fabric,muralisrini/fabric,stemlending/fabric,jimthematrix/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,stemlending/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric,binhn/fabric,manish-sethi/fabric,muralisrini/fabric,jimthematrix/fabric,stemlending/fabric,manish-sethi/fabric-sidedb,hyperledger/fabric