Refactor usage of Packages::Helm::CreateMetadataCacheWorker to not violate Rubocop rules

What does this MR do and why?

We currently have multiple places that directly use Packages::Helm::CreateMetadataCacheWorker, which violates the CodeReuse/Worker rule.

This creates inconsistent patterns and duplicated logic across different scenarios.

This MR introduces two solutions to address CodeReuse/Worker violations in Helm metadata cache synchronization:

• New Packages::Helm::BulkySyncHelmMetadataCaches service for bulk operations involving multiple packages/package_files
• New API::Helpers::Packages::Helm  helper for syncing single Helm metadata cache like what we do for npm metadata cache

Those 2 changes address all the scenarios outlined in the issue.

Database

Query all file metadata for the given package files

Raw Query

SELECT DISTINCT
    "packages_helm_file_metadata"."channel",
    "packages_helm_file_metadata"."project_id"
FROM
    "packages_helm_file_metadata"
WHERE
    "packages_helm_file_metadata"."package_file_id" IN (1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010)

Query plan: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/43736/commands/133615

Query all package files for the given packages with specific project and channel

Raw Query

SELECT
    "packages_package_files".*
FROM
    "packages_package_files"
    INNER JOIN "packages_packages" ON "packages_packages"."id" = "packages_package_files"."package_id"
    INNER JOIN "packages_helm_file_metadata" ON "packages_helm_file_metadata"."package_file_id" = "packages_package_files"."id"
WHERE
    "packages_package_files"."package_id" IN (11, 10)
    AND "packages_packages"."package_type" = 11
    AND "packages_packages"."project_id" = 4
    AND "packages_packages"."status" IN (0, 1, 5)
    AND "packages_helm_file_metadata"."channel" = 'stable'
    AND "packages_package_files"."status" = 0

Query plan: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/44043/commands/134772

References

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Screenshots or screen recordings

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How to set up and validate locally

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MR acceptance checklist

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Related to #569680 (closed)