Support dump mode

[axinging]

Dump mode enchances model debug mode in three ways:

1. Support whole model dump in different dumpLevel: 0, dump close diffs. 1, dump any diffs. 2, dump all.
2. Support ops dump.
3. Support dumpLength: -1 means all.

[cesarvspr]

I think @axinging already worked on this issue, right?

[axinging]

I think @axinging already worked on this issue, right?
@cesarvspr , Yes, the WIP pr: #6850