Fix infinite recursion for Debug::fmt

[jcdickinson]

This Pull Request fixes/closes #608.

It changes the following:

• Adds a test for stack overflow
• Removes prototype from the Debug::fmt for Object

[codecov]

Codecov Report

Merging #609 into master will increase coverage by 0.01%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##           master     #609      +/-   ##
==========================================
+ Coverage   72.51%   72.53%   +0.01%     
==========================================
  Files         179      179              
  Lines       12553    12565      +12     
==========================================
+ Hits         9103     9114      +11     
- Misses       3450     3451       +1     

Impacted Files	Coverage Δ
boa/src/builtins/object/mod.rs	40.26% <85.71%> (+1.45%)	⬆️
boa/src/builtins/value/tests.rs	100.00% <100.00%> (ø)

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[HalidOdat]

Couldn't any of these overflow for example:

let x = {};
x.itSelf = x;

the itSelf property is contained in properties and this would cause a stack overflow, right?

[jcdickinson]

prototype always overflows, I thought it valuable to get a fix in for that (because I suspect it is breaking the test262 PR) and then figure out how to approach this in a general way after some discussion.

[Razican]

Why was this closed, @jcdickinson? I would be happy to have an patial fix for stack overflows.

[jcdickinson]

@Razican I'll do a proper fix.