[llvm] [SampleProfile] Disambiguate terminology around "CS" in Eytzinger layout (NFC) (PR #215358)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-darwin` running on `doug-worker-3` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/21712

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
...
PASS: lld :: MinGW/error-limit.test (95680 of 95689)
PASS: lld :: MinGW/lib.test (95681 of 95689)
PASS: lld :: MachO/weak-reference.s (95682 of 95689)
PASS: lld :: MachO/why-live.s (95683 of 95689)
PASS: lld :: MachO/weak-definition-direct-fetch.s (95684 of 95689)
PASS: lld :: MachO/weak-definition-gc.s (95685 of 95689)
PASS: lld :: MachO/zippered.yaml (95686 of 95689)
PASS: lld :: MinGW/driver.test (95687 of 95689)
PASS: Clangd Unit Tests :: ./ClangdTests/7/12 (95688 of 95689)
TIMEOUT: Clangd Unit Tests :: ./ClangdTests/8/12 (95689 of 95689)
******************** TEST 'Clangd Unit Tests :: ./ClangdTests/8/12' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/tools/extra/clangd/unittests/./ClangdTests-Clangd Unit Tests-15275-8-12.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=12 GTEST_SHARD_INDEX=8 /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/tools/extra/clangd/unittests/./ClangdTests
--

Note: This is test shard 9 of 12.
[==========] Running 118 tests from 78 test suites.
[----------] Global test environment set-up.
[----------] 1 test from ClangdAST
[ RUN      ] ClangdAST.PreferredIncludeDirective
Built preamble of size 212216 for file /clangd-test/TestTU.m version null in 0.02 seconds
Built preamble of size 212900 for file /clangd-test/TestTUHeader.h version null in 0.01 seconds
Built preamble of size 212900 for file /clangd-test/TestTUHeader.h version null in 0.01 seconds
Built preamble of size 212760 for file /clangd-test/TestTUHeader.h version null in 0.01 seconds
[       OK ] ClangdAST.PreferredIncludeDirective (85 ms)
[----------] 1 test from ClangdAST (85 ms total)

[----------] 1 test from BackgroundIndexTest
[ RUN      ] BackgroundIndexTest.NoDotsInAbsPath
Enqueueing 1 commands for indexing
Failed to load shard: /clangd-test/root/A.cc
Indexing ../A.cc (digest:=C294D3380580062D)
Indexed ../A.cc (0 symbols, 0 refs, 1 files)
BackgroundIndex: building version 1 when background indexer is idle
BackgroundIndex: serving version 1 (232 bytes)
Enqueueing 1 commands for indexing
Failed to load shard: /clangd-test/root/B.cc
Indexing ./B.cc (digest:=C294D3380580062D)
Indexed ./B.cc (0 symbols, 0 refs, 1 files)
BackgroundIndex: building version 2 when background indexer is idle
BackgroundIndex: serving version 2 (464 bytes)
[       OK ] BackgroundIndexTest.NoDotsInAbsPath (9 ms)
[----------] 1 test from BackgroundIndexTest (9 ms total)

[----------] 2 tests from CallHierarchy
[ RUN      ] CallHierarchy.IncomingOneFileObjC
Built preamble of size 212220 for file /clangd-test/TestTU.m version null in 0.01 seconds
Built preamble of size 212220 for file /clangd-test/TestTU.m version null in 0.01 seconds

```

</details>

https://github.com/llvm/llvm-project/pull/215358