fix(boa): fixes unshift maximum size

[neeldug]

This Pull Request fixes/closes #1306.

It changes the following:

• throws TypeErrException according to spec for len + argCount > MAX_SAFE_INTEGER

[Razican]

Thanks! Looks good :) check my comment in case it makes sense

[Razican]

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,897	78,897	0
Passed	26,940	26,949	+9
Ignored	15,628	15,622	-6
Failed	36,329	36,326	-3
Panics	1	0	-1
Conformance	34.15%	34.16%	+0.01%

Fixed tests:

test/built-ins/Array/prototype/unshift/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/unshift/throws-if-integer-limit-exceeded.js (previously Ignored)
test/built-ins/Array/prototype/splice/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/splice/throws-if-integer-limit-exceeded.js (previously Ignored)
test/built-ins/Array/prototype/push/S15.4.4.7_A2_T2.js [strict mode] (previously Failed)
test/built-ins/Array/prototype/push/S15.4.4.7_A2_T2.js (previously Failed)
test/built-ins/Array/prototype/push/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/push/throws-if-integer-limit-exceeded.js (previously Ignored)
test/built-ins/Map/prototype/keys/returns-iterator.js (previously Panic)

[Razican]

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,897	78,897	0
Passed	26,940	26,945	+5
Ignored	15,628	15,622	-6
Failed	36,329	36,330	+1
Panics	1	0	-1
Conformance	34.15%	34.15%	+0.01%

Fixed tests:

test/built-ins/Array/prototype/unshift/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/unshift/throws-if-integer-limit-exceeded.js (previously Ignored)
test/built-ins/Array/prototype/splice/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/splice/throws-if-integer-limit-exceeded.js (previously Ignored)
test/built-ins/Map/prototype/keys/returns-iterator.js (previously Panic)

Broken tests:

test/built-ins/Array/prototype/push/throws-if-integer-limit-exceeded.js [strict mode] (previously Ignored)
test/built-ins/Array/prototype/push/throws-if-integer-limit-exceeded.js (previously Ignored)

It seems there is one new test broken (in both strict and non-strict mode), could you check why?