Refactor qdb

[elicn]

qdb refactored from ground up, overall improving feature stability, reliability and maintainability.
Note: some debug prints are still present; waiting for feedback.

Highlights:

• Misc cosmetic improvements
• Revised classes and mixin hierarchy to be more intuitive
• Consolidated and de-duplicated common functionality
• Heavily commented and documented the code, in addition to annotations
• Branch prediction greatly improved
  • Assembly analysis now based on Capstone objects rather than unreliable string parsing
  • More corner cases are now covered
  • Prediction target got more accurate
• Going backwards greatly improved
  • Now also reverting memory layout in addition to memory contents
  • Snapshot memory footprint has been reduced
• qdb commands can now evaluate compound expressions, e.g. x/8i ($pc + $sp + (4 * $r1))
• Rewrote all tests to reflect meaningful scenarios
• Bug fixes

TODO:

• Redesign classes hierarchy
• Improve snapshots by covering more operating system resources, such as file descriptors, etc.
• Make existing commands more resemble to their gdb equivalents
• Support more commands

Screenshot 1: context dump, predicting branch taken upwards

Screenshot 2: examine command taking an expression as its argument