feat(bitbucket): support task autocomplete (#30901)

docs/usage/configuration-options.md

lib/config/options/index.ts

lib/modules/platform/bitbucket/index.spec.ts

lib/modules/platform/bitbucket/index.ts

lib/modules/platform/bitbucket/schema.ts

lib/modules/platform/types.ts

lib/workers/repository/update/pr/index.ts