Set an executable page at the top of the stack

[mohanson]

When this feature is enabled, the top of the stack will be marked as an executable memory page. If the heap or stack attempts to write data to this area, ckb-vm will return an error due to the wxorx rules.

The purpose of this feature is to use it in dapp's testcase, which can reduce the occurrence of overlap.

Note that we have several test cases that use too much heap, which will trigger overlap checks.

[XuJiandong]

The position should be at symbol "_end": https://man7.org/linux/man-pages/man3/end.3.html
Since we don't use brk the "_end" can be treated as end of stack.

[mohanson]

The method you mentioned is the same as the ckb-vm-pprof https://github.com/nervosnetwork/ckb-standalone-debugger/blob/develop/ckb-vm-pprof/src/lib.rs#L217-L221

You can use PProfMachine directly without adding the same functionality to the ckb-vm project.