Support overriding the arguments variable

[AnnikaCodes]

This eliminates a number of panics in the Test262 suite.

This Pull Request works on #817.

It changes the following:

• allows name reuse when declaring the arguments variable

[codecov]

Codecov Report

Merging #1049 (7097185) into master (624d03d) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1049   +/-   ##
=======================================
  Coverage   58.31%   58.31%           
=======================================
  Files         172      172           
  Lines       12007    12007           
=======================================
  Hits         7002     7002           
  Misses       5005     5005           

Impacted Files	Coverage Δ
boa/src/object/gcobject.rs	67.00% <100.00%> (ø)

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[Razican]

Thanks!
I have another PR almost ready that complements this, and should reduce the count of panics too :)

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,497	78,497	0
Passed	24,548	24,548	0
Ignored	15,585	15,585	0
Failed	38,364	38,364	0
Panics	45	28	-17
Conformance	31.27	31.27	0.00%

Looking very good!