[clang] [CIR] Implement simple folding for integer casts (PR #174861)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-5` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/33812

<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)
...
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using llvm-objcopy: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/llvm-objcopy
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using clang: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/clang
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using ld.lld: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/ld.lld
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using lld-link: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/lld-link
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using ld64.lld: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/ld64.lld
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using wasm-ld: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/wasm-ld
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using llvm-ar: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/llvm-ar
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/util.py:363: note: using SDKROOT: '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk'
llvm-lit: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/llvm/utils/lit/lit/llvm/config.py:561: note: using clang: /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/clang
llvm-lit: /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/cross-project-tests/lit.cfg.py:321: fatal: Running lldb tests requires the packaging package
FAILED: [code=2] CMakeFiles/check-all /Users/buildbot/buildbot-root/aarch64-darwin/build/CMakeFiles/check-all 
cd /Users/buildbot/buildbot-root/aarch64-darwin/build && /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/bin/python3.9 /Users/buildbot/buildbot-root/aarch64-darwin/build/./bin/llvm-lit --verbose --timeout=900 /Users/buildbot/buildbot-root/aarch64-darwin/build/utils/mlgo-utils /Users/buildbot/buildbot-root/aarch64-darwin/build/projects/cross-project-tests /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/tools/extra/include-cleaner/test /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/tools/extra/clangd/test/../unittests /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/tools/extra/clangd/test /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/tools/extra/test /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/test /Users/buildbot/buildbot-root/aarch64-darwin/build/utils/lit /Users/buildbot/buildbot-root/aarch64-darwin/build/test
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/174861