added effective_length to MultiStateSamplerAnalyzer #1585

Job	Run time
macOS-latest, py-3.8, OpenMM-7.7, pymbar-4	34m 35s
ubuntu-latest, py-3.8, OpenMM-7.7, pymbar-4	21m 32s
macOS-latest, py-3.8, OpenMM-8.0, pymbar-4	33m 31s
ubuntu-latest, py-3.8, OpenMM-8.0, pymbar-4	25m 41s
macOS-latest, py-3.9, OpenMM-7.7, pymbar-4	35m 4s
ubuntu-latest, py-3.9, OpenMM-7.7, pymbar-4	24m 2s
macOS-latest, py-3.9, OpenMM-8.0, pymbar-4	34m 45s
ubuntu-latest, py-3.9, OpenMM-8.0, pymbar-4	28m 34s
macOS-latest, py-3.10, OpenMM-8.0, pymbar-4	32m 45s
ubuntu-latest, py-3.10, OpenMM-8.0, pymbar-4	19m 56s
ubuntu-latest, py-3.10, OpenMM-dev, pymbar-4	21m 47s
windows-latest, py-3.10, OpenMM-8.0, pymbar-4	30m 12s
ubuntu-latest, py-3.10, OpenMM-8.0, pymbar-3	24m 36s
	6h 7m 0s

Provide feedback