ModelingTools: Add UMultiSelectionMeshEditingTool to hold common interface requirements and functions that pertain to modeling mode MultiSelectionTools.
#rb semion.piskarev
#rnx
#jira none
#preflight 619c66d5c3287aab27e12c73
#ROBOMERGE-AUTHOR: lonnie.li
#ROBOMERGE-SOURCE: CL 18269697 in //UE5/Release-5.0/... via CL 18269713
#ROBOMERGE-BOT: STARSHIP (Release-Engine-Staging -> Release-Engine-Test) (v895-18170469)
[CL 18269717 by lonnie li in ue5-release-engine-test branch]