[RnD][LLVM15][MIPS][libunwind] Port fix frame_layout test from llvm-test-suite · Pull Request !229 · OpenHarmony/third_party_llvm-project

### Issue

https://gitee.com/open_harmony/dashboard?issue_id=I6QKXU

### Reason (Purpose, Solved Problem)

It is needed to port libunwind fixes for MIPS target !111 from llvm12 to llvm15 (current master)

### Description

Our llvm-12 branch contains fixes for MIPS target that should be ported to newer toolchain.

This PR contains 3 commits related to the frame_layout test fix.
-    Annotate previously proposed OHOS-local changes for future ease of porting.
-    Fix the root cause of the issue: filling the FP registers buffer;
-    Fix `__unw_getcontext` and `libunwind::Registers_mips_o32::jumpto()` so we
    are able to implement a separate test in llvm-test-suite to check the fix
    proposed in the previous commit. It turns out that the frame_layout test
    find the error occasionally, so we need to have a separate test for that.
    Given that, we also include this commit in the current PR.

### Test (Local test)

CI

### Need to cherry-pick to release (eg：monthly_20221018, OpenHarmony-3.2-Beta5 ...) branch？

- [ ] yes，branch list:
- [x] no

类型	指派人员	状态
审查	hhj Pavel Kosov 已审查通过	已完成 (1/1人)
测试	openharmony_ci 已测试通过	已完成 (1/1人)

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