refactor(i18n): Prepare old resources for deprecation. Simplify resource maps.

[skrustev]

Description

• Introduce union types for the Calendar, Date Picker and Date Range Picker resourceStrings properties setter. The getter type remains unchanged until to avoid breaking changes for now, but it will contain the new resources as well for migration.
• Simplify resource map handling
• Add Date Picker resource map
• Update resource names used in all components ahead of time to use new resources
• Tagged deprecated interfaces and old EN resources

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that causes existing functionality to change)
• Documentation update
• Refactoring (code improvements without functional changes)

Related Issues

Resolves #2166

Testing

• Please make sure that old behavior remains unchanged and new it allows for switch to new resources.

Checklist

• My code follows the project's coding standards
• I have tested my changes locally
• I have updated documentation if needed
• Breaking changes are documented in the description