Create a wrapper for Rails.cache with metrics support

What does this MR do and why?

Contributes to #383458 (closed)

Problem

We don't have hit-rate and time of generation metrics for Redis cache

Solution

Create a in-place replacement for Rails.cache call with metrics integrations

Roadmap

Step	MR
Refactor Gitlab::Cache::Metrics	!111345 (merged)
Create Gitlab::Cache::Client	👈 this MR

Example

https://gitlab.com/gitlab-org/gitlab/blob/80ff2c3140970dedbae17639c9eea2e086682848/lib/api/files.rb#L52

Before

Rails.cache.fetch("blob_content_sha256:#{user_project.full_path}:#{@blob.id}") do
  @blob.load_all_data!

  Digest::SHA256.hexdigest(@blob.data)
end

After

cache_client = Gitlab::Cache::Client.meta(
  feature_category: :source_code_management,
  cache_identifier: "#{self.class}#content_sha"
)

cache_client.fetch("blob_content_sha256:#{user_project.full_path}:#{@blob.id}") do
  @blob.load_all_data!

  Digest::SHA256.hexdigest(@blob.data)
end

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.