refactor: remove Default scheduler implementation as it not used anymore

[AviralGoelAMD]

Proposed changes

The universal GEMM's memory pipeline (software pipeline) has a "default" scheduler implementation for scheduling data computation instructions. This implementation is no longer used and are most likely remnants of early version of the example.

This PR removes the dead code.

Checklist

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• I have added tests relevant to the introduced functionality, and the unit tests are passing locally
• I have added the test to REGRESSION_TESTS list defined at the top of CMakeLists.txt in tests/CMakeLists.txt, IF the test takes more than 30 seconds to run.
• I have added inline documentation which enables the maintainers with understanding the motivation
• I have removed the stale documentation which is no longer relevant after this pull request
• (If this change is user-facing) I have added release notes which provide the end users with a brief summary of the improvement from this pull request
• I have run clang-format on all changed files
• Any dependent changes have been merged

Discussion

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[Copilot]

Pull request overview

This PR removes the unused "Default" scheduler implementation from the universal GEMM's memory pipeline software pipeline. The Default scheduler was likely a remnant from early development and is no longer used in the codebase.

Changes:

• Removed the Default scheduler implementation from block-level GEMM operations
• Updated the default scheduler to Intrawave in the base GEMM pipeline problem
• Removed unused template parameter and associated conditional logic from the universal GEMM kernel
• Fixed a template specialization mismatch in the AQuant pipeline (was incorrectly labeled as Interwave, now correctly Intrawave)
• Added helpful documentation comments explaining barrier instructions

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
include/ck_tile/ops/gemm/block/block_universal_gemm_as_bs_cr.hpp	Removed the BlockGemmImpl<GemmPipelineScheduler::Default> specialization (83 lines) and added clarifying comments for barrier instructions
include/ck_tile/ops/gemm/pipeline/gemm_pipeline_problem.hpp	Changed the default scheduler from Default to Intrawave in GemmPipelineProblemBase
include/ck_tile/ops/gemm/kernel/universal_gemm_kernel.hpp	Removed unused UseDefaultScheduler template parameter and associated conditional logic from RunGemm
include/ck_tile/ops/gemm_quant/pipeline/gemm_aquant_pipeline_ag_bg_cr_mem.hpp	Fixed template specialization from Interwave to Intrawave to match actual usage

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