[clang] [Clang] Bugfixes and improved support for `AttributedType`s in lambdas (PR #85325)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `clang` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/5052

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: SemaCXX/lambda-attributes.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/20/include -nostdsysteminc -std=c++23 -fsyntax-only -verify /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp
+ /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/20/include -nostdsysteminc -std=c++23 -fsyntax-only -verify /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp
error: 'expected-warning' diagnostics seen but not expected: 
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp Line 18: 'preserve_most' calling convention is not supported for this target
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp Line 29: 'preserve_most' calling convention is not supported for this target
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp Line 33: 'cdecl' calling convention is not supported for this target
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/SemaCXX/lambda-attributes.cpp Line 40: 'preserve_most' calling convention is not supported for this target
  Line 45: 'preserve_most' calling convention is not supported for this target
  Line 48: 'preserve_most' calling convention is not supported for this target
  Line 53: 'preserve_most' calling convention is not supported for this target
7 errors generated.

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/85325