feat: add C implementation of `stats/base/dists/gumbel/mean` #10211

Job	Run time
Add initial reaction	3s
Update copyright header years / Update Copyright Years	27s
Check for required files	0s
Auto-fix lint errors	0s
Print a list of available slash commands	0s
Merge changes from develop branch into this PR	0s
Rebase this PR on top of develop branch	0s
Remove in-progress label	3s
	33s

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