Add support of decal maps

Today the editor allows to create decals but only decal meshes are supported (https://doc.babylonjs.com/features/featuresDeepDive/mesh/decals#mesh-decals).

For performance reason the user should be able to create decals using decal maps (https://doc.babylonjs.com/features/featuresDeepDive/mesh/decals#texture-decals-or-decal-maps)

The tool in the inspector should be able to provide both way to create decals. Decal meshes and decal maps have their own limitations so both should be supported depending on the usage

@Ezardy