[llvm] [llubi] Extract reusable methods of InstExecutor into ExecutorBase (PR #186976)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/20535

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

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: LLVM :: CodeGen/AMDGPU/directive-amdgcn-target.ll (108739 of 108750)
PASS: Clang :: Driver/amdgpu-mcpu.cl (108740 of 108750)
PASS: LLVM :: tools/llvm-readobj/ELF/mips-abiflags.test (108741 of 108750)
PASS: Clang :: Driver/fsanitize.c (108742 of 108750)
PASS: LLVM :: CodeGen/ARM/build-attributes.ll (108743 of 108750)
PASS: LLVM :: tools/llvm-readobj/ELF/file-header-machine-types.test (108744 of 108750)
PASS: Clang :: Driver/x86-target-features.c (108745 of 108750)
PASS: Clang :: Driver/arm-cortex-cpus-2.c (108746 of 108750)
PASS: Clang :: Preprocessor/predefined-arch-macros.c (108747 of 108750)
PASS: Clang :: Preprocessor/riscv-target-features.c (108748 of 108750)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=12656.006524

```

</details>

https://github.com/llvm/llvm-project/pull/186976