remove the need for `meshconfig` when building initial discovery requests.

[believening]

We have not used meshconfig historically or currently, and need to check if it can be removed.

slime/framework/bootstrap/adsc/adsc.go

Lines 10 to 12 in 0bdcb6c

	out = append(out, &discovery.DiscoveryRequest{
	TypeUrl: collections.IstioMeshV1Alpha1MeshConfig.String(),
	})