[clang-format] Fix consecutive alignments in #else blocks

Since 3.8 or earlier, clang-format has been lumping all #else, #elif,
etc blocks together when doing whitespace replacements and causing
consecutive alignments across #else blocks.

Commit c0779756 partially addressed the problem but also triggered
"regressions".

This patch fixes the root cause of the problem and "reverts" c0779756
(except for the unit tests).

Fixes #36070.
Fixes #55265.
Fixes #60721.
Fixes #61498.

Differential Revision: https://reviews.llvm.org/D150057