Add `to_xml` method to Topology #1358

Job	Run time
GMSO Tests (macOS-latest, 3.9, 2)	25m 6s
GMSO Tests (macOS-latest, 3.9, 2)	25m 6s
Bleeding Edge mosdef Tests for GMSO	11m 54s
Bleeding Edge mosdef Tests for GMSO	11m 54s
GMSO Tests (macOS-latest, 3.10, 2)	36m 22s
GMSO Tests (macOS-latest, 3.10, 2)	36m 22s
GMSO Tests (macOS-latest, 3.11, 2)	35m 6s
GMSO Tests (macOS-latest, 3.11, 2)	35m 6s
GMSO Tests (ubuntu-latest, 3.9, 2)	25m 46s
GMSO Tests (ubuntu-latest, 3.9, 2)	25m 46s
GMSO Tests (ubuntu-latest, 3.10, 2)	22m 33s
GMSO Tests (ubuntu-latest, 3.10, 2)	20m 39s
GMSO Tests (ubuntu-latest, 3.11, 2)	26m 14s
GMSO Tests (ubuntu-latest, 3.11, 2)	26m 14s
Build Docker Image	0s
Build Docker Image	0s
	6h 4m 8s

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