Refactor environment stack to remove some panics

[raskad]

Thie PR refactors the environment stack to avoid panics. The main change is to put the global declarative environment in a separete field instead of on the stack itself. That way we can safeley avoid panics.

There was only a very slight difference in benchmarks, but I think reducing the panics is worth it either way.
After running the benchmarks a few times they look pretty good:

Before:

RESULT Richards 60.6
RESULT DeltaBlue 63.4
RESULT Crypto 74.4
RESULT RayTrace 202
RESULT EarleyBoyer 186
RESULT RegExp 61.1
RESULT Splay 199
RESULT NavierStokes 175
SCORE 111

After:

RESULT Richards 65.8
RESULT DeltaBlue 69.6
RESULT Crypto 77.1
RESULT RayTrace 201
RESULT EarleyBoyer 199
RESULT RegExp 59.9
RESULT Splay 226
RESULT NavierStokes 176
SCORE 116

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	48,212	48,212	0
Passed	42,875	42,875	0
Ignored	1,413	1,413	0
Failed	3,924	3,924	0
Panics	0	0	0
Conformance	88.93%	88.93%	0.00%

[jedel1043]

Really nice enhancement!

[HalidOdat]

Nice work, looks good to me! :)