hostmetricsreceiver: use gopsutil cached boot time (#32126) #9

Job	Run time
windows-unittest-matrix (receiver-0)	17m 21s
windows-unittest-matrix (receiver-1)	17m 27s
windows-unittest-matrix (processor)	13m 32s
windows-unittest-matrix (exporter)	26m 38s
windows-unittest-matrix (extension)	17m 4s
windows-unittest-matrix (internal)	16m 37s
windows-unittest-matrix (pkg)	11m 22s
windows-unittest-matrix (cmd)	21m 26s
windows-unittest-matrix (other)	22m 13s
windows-unittest	3s
	2h 43m 43s

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