feat: add `math/base/special/floornf` #23620

Job	Run time
Add initial reaction	6s
Update copyright header years	0s
Check for required files	0s
Rebase this PR on top of develop branch	0s
Merge changes from develop branch into this PR / Merge Develop into PR Branch	1m 50s
Post a comment with make command instructions	0s
Auto-fix lint errors	0s
Print a list of available slash commands	0s
Remove in-progress label	3s
	1m 59s

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