Revert DSE workarounds, this was causing some problems in main.

Revert "[clangd] Fix builds after 4ddae8b9"

This reverts commit ae42196b.

Revert "[clangd] Fix test failure when it's built with compiler flags unknown by clang"

This reverts commit 21f3dfbc.

Revert "[cmake] Disable GCC lifetime DSE"

This reverts commit d5cce0a7.

Revert "[clang-tidy][test] Add trailing -- to suppress compile_commands.json read"

This reverts commit 57262bbd.