odb: encapsulate inst module assignment

[naveenvenk17]

Summary

• route module parent changes through _dbInst helper methods instead of direct module_ writes
• emit inDbPostInstParentChange when an instance is reparented between modules
• keep quiet module assignment for serialization, creation, and removal paths that must not fire callbacks

Tests

• PASS: bazelisk build --jobs=4 --local_cpu_resources=4 //src/odb/src/db:db
• BLOCKED: bazelisk test --jobs=4 --local_cpu_resources=4 //src/dbSta/test:sdc_modinst_slash-tcl_test on the Ubuntu 22.04 GCP VM fails before test execution while linking openroad with unresolved __isoc23_* glibc symbols from the Bazel LLVM/sysroot toolchain.

[gemini-code-assist]

Code Review

This pull request encapsulates the module_ member variable of _dbInst by making it private and introducing getter and setter methods (getModuleId, setModule, and setModuleQuiet). The setModule method handles triggering the inDbPostInstParentChange callback when an instance's parent module changes. Consequently, direct accesses and modifications to module_ across dbBlock.cpp, dbInst.cpp, and dbModule.cpp have been updated to use these new encapsulated methods. Additionally, a new helper function rebuildDbInstModuleHash was introduced in dbBlock.cpp to reconstruct the instance module hash map. There are no review comments, so I have no feedback to provide.