[comgr][hotswap] scale hotswap rewrites for large code objects (amd-staging companion)

[harsh-amd]

Purpose

Direct-to-amd-staging companion for the focused stacked review in #3348.

This PR exists so the full amd-staging CI workflows evaluate the cumulative
remaining stack through #3348. #3345 and #3346 are already merged. Please use #3348 for
review of the large-object scaling patch itself; its base is #3347 so that
focused diff contains only one stack entry.

Included stack

• [comgr][hotswap] eliminate add-pc from far hotswap trampolines #3347 — eliminate add-pc from far hotswap trampolines
• [comgr][hotswap] scale hotswap rewrites for large code objects #3348 — scale hotswap rewrites for large code objects

This companion should not merge before #3347. When #3347 lands in
amd-staging, GitHub will reduce this PR to the remaining focused change.

Local validation

• rebased onto current amd-staging after [comgr][hotswap] make gfx1250 semantic rewrites fail-safe #3346 was squash-merged
• git range-diff confirms every reviewed patch is unchanged, and the old and
  rebased amd/comgr trees are identical
• git-clang-format --diff is clean; both rewritten formatter checks pass in CI
• release check-comgr at the final rebased stack tip: all unit tests, 97/97
  supported LIT tests (11 unsupported), and 31/31 CTests passed
• ASan at the final rebased stack tip: all unit tests and 97/97 supported LIT
  tests passed

Resolved external CI issue

The previous Linux::release / Build failure occurred after LLVM and COMGR
built successfully, in the separately checked-out rocm-systems develop
branch while compiling libhsakmt: _GNU_SOURCE was defined after system
headers, leaving secure_getenv undeclared. The approved upstream fix is
ROCm/rocm-systems#8555, which has now merged. No llvm-project source change was
needed; the newly triggered Linux job includes that upstream fix.