[re #12345] Migrated rest of the jira services to use services from core package

Rest of the Jira services were migrated to using the services from package core.

• Created couple of methods in core package needed to loading existing data from DB
• Removed remaining unused services
• Added method to core DateMapper for parsing special format of DateTime (retrieved from Jira API)

After this MR, all services used in jira package are using the architecture from core package. Also thanks to that migration, we achieved:

• No need to check manually if object already exists (the core methods handle that automatically)
• We optimised API calls (now, every information from API we fetch only ONCE)
• The code is more clean and readable - and even the size of the files were reduced