feat: add C implementation for `stats/base/dists/chi/logpdf` #21420

Job	Run time
Add initial reaction	6s
Update copyright header years	0s
Post a comment with make command instructions	0s
Auto-fix lint errors	0s
Merge changes from develop branch into this PR / Merge Develop into PR Branch	1m 37s
Rebase this PR on top of develop branch	-1s
Check for required files	-1s
Print a list of available slash commands	-1s
Remove in-progress label	3s
	1m 43s

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