Add fastbin unit tests

[gsingh93]

No description provided.

[codecov-commenter]

Codecov Report

Merging #1295 (97ca167) into dev (dac5340) will decrease coverage by 0.03%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##              dev    #1295      +/-   ##
==========================================
- Coverage   57.19%   57.16%   -0.04%     
==========================================
  Files         188      189       +1     
  Lines       20716    20715       -1     
  Branches     1916     1918       +2     
==========================================
- Hits        11849    11842       -7     
- Misses       8400     8409       +9     
+ Partials      467      464       -3     

Impacted Files	Coverage Δ
pwndbg/commands/__init__.py	67.59% <ø> (-2.24%)	⬇️
pwndbg/__init__.py	87.50% <88.88%> (-3.41%)	⬇️
pwndbg/color/theme.py	100.00% <100.00%> (ø)
pwndbg/commands/heap.py	66.80% <100.00%> (-0.32%)	⬇️
pwndbg/exception.py	55.55% <100.00%> (ø)
pwndbg/gdblib/argv.py	88.23% <100.00%> (ø)
pwndbg/lib/heap/helpers.py	100.00% <100.00%> (ø)
pwndbg/ui.py	75.00% <100.00%> (ø)
pwndbg/commands/vmmap.py	41.30% <0.00%> (-2.18%)	⬇️
... and 5 more

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