cache: use `platform` as the cache keys

[jamietanna]

It was recently noticed that we use a camelCase variant of the platform name in RepoCacheData only for bitbucketServer.

bitbucketServer should be cased as bitbucket-server (

renovate/lib/constants/platforms.ts

Lines 1 to 13 in db824b9

	export const PLATFORM_HOST_TYPES = [
	'azure',
	'bitbucket',
	'bitbucket-server',
	'codecommit',
	'forgejo',
	'gerrit',
	'gitea',
	'github',
	'gitlab',
	'local',
	] as const;

) as that matches the platform name.

We should fix this, so it's a 1-1 mapping between a platform name and a cache key or make sure that there's a way to pass a platform and receive the cache settings for that platform.

This can either be done as a breaking change (in the next major) or as a non-breaking change for now, and then made breaking in the future, for consistency.