[clang] Revert "Reapply "[Clang][Sema] Refactor collection of multi-level template argument lists (#106585, #111173)" (#111852)" (PR #115159)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-linux` running on `premerge-linux-1` while building `clang` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/13862

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -std=c++20 -fsyntax-only -verify /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp
+ /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -std=c++20 -fsyntax-only -verify /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp
error: 'expected-error' diagnostics seen but not expected: 
  File /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp Line 73: static assertion failed due to requirement 'A<int>::B<int &>::y == 4'
  File /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp Line 77: static assertion failed due to requirement 'A<int>::x<int &> == 4'
error: 'expected-note' diagnostics seen but not expected: 
  File /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp Line 73: expression evaluates to '3 == 4'
  File /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/CXX/temp/temp.decls/temp.spec.partial/temp.spec.partial.member/p2.cpp Line 77: expression evaluates to '3 == 4'
4 errors generated.

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/115159