Add shared specs when precision is passed in for Integer#floor, Float#floor and Integer#ceil, Float#ceil #1723

Job	Run time
RuboCop	25s
specs (ubuntu, 3.0.6)	1m 29s
specs (ubuntu, 3.1.4)	1m 28s
specs (ubuntu, 3.2.2)	1m 24s
specs (ubuntu, 3.3.0)	1m 23s
specs (macos, 3.0.6)	1m 21s
specs (macos, 3.1.4)	1m 45s
specs (macos, 3.2.2)	1m 8s
specs (macos, 3.3.0)	1m 10s
specs (windows, 3.0.6)	3m 38s
specs (windows, 3.1.4)	4m 24s
specs (windows, 3.2.2)	5m 15s
specs (windows, 3.3.0)	5m 32s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 20s
	31m 42s

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