[core] inlining Interval methods and related operators #201

Job	Run time
macOS Sonoma Python 3.13 arm64	6m 1s
macOS Sonoma Python 3.12 arm64	6m 50s
macOS Sonoma Python 3.11 arm64	5m 15s
macOS Ventura Python 3.10 arm64 (cross)	11m 40s
macOS Ventura Python 3.9 arm64 (cross)	17m 52s
macOS Ventura Python 3.8 arm64 (cross)	14m 27s
macOS Ventura Python 3.7 arm64 (cross)	15m 31s
macOS Ventura Python 3.6 arm64 (cross)	17m 7s
macOS Ventura Python 3.13 x86_64	19m 15s
macOS Ventura Python 3.12 x86_64	11m 16s
macOS Ventura Python 3.11 x86_64	18m 11s
macOS Ventura Python 3.10 x86_64	11m 13s
macOS Ventura Python 3.9 x86_64	13m 52s
macOS Ventura Python 3.8 x86_64	17m 35s
macOS Ventura Python 3.7 x86_64	11m 57s
macOS Ventura Python 3.6 x86_64	12m 31s
	3h 30m 33s

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