[lldb/crashlog] Add `--no-parallel-image-loading` hidden flag (#94513)

This patch adds the `--no-parallel-image-loading` to the crashlog
command. By default, image loading will happen in parallel in the
crashlog script however, sometimes, when running tests or debugging the
crashlog script itself, it's better to load the images sequentially.

As its name suggests, this flag will disable the default image loading
behaviour to load all the images sequencially in the main thread.

Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>