FINERACT-2745: Deprecate and remove obsolete MIX XBRL reporting module

[DhroovSankla]

Description

During recent refactoring of JAX-RS response handling in the Mix Report module (FINERACT-2651 / PR #6017 and FINERACT-2670 / PR #6090), legacy technical debt was identified—specifically deprecated Java dependencies (such as ScriptEngine) and reliance on an obsolete external reporting standard (MIX XBRL).

Following a discussion thread on the official Apache DEV mailing list, community consensus was reached to deprecate and completely remove the MIX XBRL capability from upcoming releases to reduce technical debt and streamline build dependencies.

This PR cleanly removes the fineract-mix module, its configuration scans, client helper libraries, integration tests, and database schema artifacts.

Summary of Changes

• Module Deletion: Completely removed the fineract-mix subproject directory.
• Gradle Configurations: Removed :fineract-mix from settings.gradle, root build.gradle, provider dependencies.gradle, and fineract-war/build.gradle.
• Scan Path Cleanups: Removed "org.apache.fineract.mix.domain" scan paths and patterns from JdbcConfig.java and JPAConfig.java.
• Security Cleanups: Deleted matching patterns and authorities (READ_MIX_TAXONOMY, CREATE_MIX_TAXONOMY, etc.) from SecurityConfig.java.
• Client Helpers: Cleaned up feign client and util client helper API registrations in FineractFeignClient.java and FineractClient.java.
• Tests: Deleted all MIX XBRL integration tests (XBRLIntegrationTest.java) and Cucumber features (mix.report.feature).
• Database Schema: Added a new Liquibase migration 0243_remove_mix_module.xml to drop the tables mix_taxonomy, mix_taxonomy_mapping, and mix_xbrl_namespace, and to delete the legacy UPDATE_XBRLMAPPING permission code from m_permission.

Verification

• Local build compilation and test compilation completed successfully.
• Code style formatting checks passed successfully (spotlessCheck).