[rocm-libraries] ROCm/rocm-libraries#6528 (commit aa81df5)

[CK][CK_TILE] Fix dispatcher cpp tests - registry key mismatch and string assertions (#6528)

## Motivation

CPP tests in dispatcher were failing due to a mismatch in registry key
and string representation.

## Technical Details
Bug 1 - Registry key mismatch: The registry stored kernels using
get_name() but lookups used encode_identifier(), causing all registry
lookups to fail. Fixed by changing registry.cpp:58 to use
encode_identifier() for storage.
Bug 2 - String representation changes: Tests checked for
"persist"/"nopers" substrings, but the code emits "True"/"False". Fixed
by replacing brittle substring checks with comparison-based assertions
in test_kernel_key.cpp and test_kernel_key_extended.cpp.

## Test Plan

Tested with CPP tests in dispatcher

## Test Result

Validation: All three core cpp tests now pass:
  - test_kernel_key - 6/6 tests passing
  - test_kernel_key_extended - 25/25 tests passing
  - test_registry - 8/8 tests passing

## Submission Checklist

- [ x] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>