FINERACT-1398: Standardize charset and collation defaults

[airajena]

Summary

This PR standardizes MySQL/MariaDB charset/collation defaults for Fineract to:

• Charset: utf8mb4
• Collation: utf8mb4_unicode_ci

It applies the standard to database creation paths, runtime datatable creation SQL, and Liquibase-managed tenant/tenant-store databases.

What Changed

1. Database creation tasks updated
2. Datatable DDL standardized
3. Liquibase migrations added
4. Unit test added

Validation Performed

• ./gradlew :fineract-provider:test --tests org.apache.fineract.infrastructure.dataqueries.service.DatatableWriteServiceImplTest
• ./gradlew spotlessApply spotbugsMain spotbugsTest checkstyleMain checkstyleTest

All passed locally.

Backward Compatibility / Risk

• No API contract changes.
• No functional change to business workflows.
• Scope is limited to DB charset/collation defaults and datatable DDL generation.
• Migration is idempotent in practice for target DB engines and is safe for incremental rollout.

Notes

• This PR focuses on runtime/schema defaults and Liquibase migration paths for MySQL/MariaDB.
• Existing historical/sample SQL files were not bulk-rewritten in this PR to keep scope tight and reviewable.