[llvm] [AArch64][GlobalISel] Remove fconstant_to_constant, moving it to reg-bank-select. (PR #194778)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

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

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/46506

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

```
Step 6 (test-build-unified-tree-check-flang) failure: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
...
PASS: Flang :: Driver/linker-flags.f90 (4445 of 4455)
PASS: Flang :: Driver/target-cpu-features.f90 (4446 of 4455)
PASS: Flang :: Driver/mrecip.f90 (4447 of 4455)
PASS: Flang :: Driver/fveclib.f90 (4448 of 4455)
PASS: Flang :: Driver/nostdlib.f90 (4449 of 4455)
PASS: Flang :: Driver/mcmodel.f90 (4450 of 4455)
PASS: Flang :: Driver/options-loongarch.f90 (4451 of 4455)
PASS: Flang :: Driver/fopenmp.f90 (4452 of 4455)
PASS: Flang :: Driver/linker-options.f90 (4453 of 4455)
PASS: Flang :: Driver/omp-driver-offload.f90 (4454 of 4455)
command timed out: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2586.339538

```

</details>

https://github.com/llvm/llvm-project/pull/194778