Fix dashboard panels distinct functions

[azrikahar]

Fixes #11574

Context

When we select Count (Distinct) aggregate function for applicable panels, the value is sent as count_distinct (snake_case):

directus/app/src/panels/metric/index.ts

Lines 83 to 84 in 051d425

	text: 'Count (Distinct)',
	value: 'count_distinct',

However the API expects countDistinct (camelCase):

directus/api/src/utils/apply-query.ts

Lines 662 to 664 in 051d425

	if (operation === 'countDistinct') {
	dbQuery.countDistinct(`${collection}.${field}`, { as: `countDistinct->${field}` });
	}

Before

It should show aggregate functiosn on two numbers, 20 and 30. 3rd number is not distinct, hence it should be omitted. But since the functions are the wrong case, they were never applied and the API returns empty result (blank UI).

After