Actualize Prometheus metrics collecting

[Zhaars]

Actualizing Prometheus metrics collection.

Added new metrics:

• acra_decryptions_total labels {"status": [ "success", "fail"], "type": [ "acrastruct", "acrablock", "acrablock_searchable", "acrastruct_searchable"],}
• acra_encryptions_total labels {"status": [ "success", "fail"], "type": [ "acrastruct", "acrablock", "acrablock_searchable", "acrastruct_searchable"],}
• acra_tokenizations_total labels {"status": [ "success", "fail"], "token_type": "{token_type}"}
• acra_detokenizations_total abels {"status": [ "success", "fail"], "token_type": "{token_type}"}

Previously used metrics are left as they are to save backward compatibility and marked as deprecated.

Checklist

• [x] Change is covered by automated tests
• [ ] The coding guidelines are followed
• [] Public API has proper documentation in the Acra documentation site or has PR on documentation repository with new changes
• [ ] CHANGELOG.md is updated (in case of notable or breaking changes)
• [x] CHANGELOG_DEV.md is updated
• [ ] Benchmark results are attached (if applicable)
• are up-to-date (in case of API changes)