fuzz: double the IOs to remove for every loop

fuzz: double the IOs to remove for every loop

Instead of removing IO instructions one by one, we can try deleting multiple
instructions at once. According to the locality of reference, we double the
number of instructions to remove for the next round and recover it to one
once we fail.

This patch is usually significant for large input.

Test with quadrupled trace input at:
  https://bugs.launchpad.net/qemu/+bug/1890333/comments/1

Patched 1/6 version:
  real  0m45.904s
  user  0m16.874s
  sys   0m10.042s

Refined version:
  real  0m11.412s
  user  0m6.888s
  sys   0m3.325s

Signed-off-by: Qiuhao Li <Qiuhao.Li@outlook.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <SYCPR01MB350280A67BB55C3FADF173E3FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>