Revert "[libFuzzer] add an experimental flag -experimental_len_control=1 that...

Revert "[libFuzzer] add an experimental flag -experimental_len_control=1 that sets max_len to 1M and tries to increases the actual max sizes of mutations very gradually. Also remove a bit of dead code"

This reverts commit r289998.

See comment:
https://reviews.llvm.org/rL289998

llvm-svn: 290043