bump gc threshold

[jasonwilliams]

As mentioned in #3896, Boa's GC threshold is set too low. This was causing too many GC collections before the interpreter even started running.

We see an improvement to the 2.

Benchmark main: ./target/release/boa
  Time (mean ± σ): 2.2 ms ± 0.2 ms [User: 0.6 ms, System: 0.1 ms]
  Range (min … max): 2.0 ms … 3.4 ms 827 runs

Benchmark PR: ./target/release/boa
  Time (mean ± σ):       2.1 ms ±   0.1 ms    [User: 0.6 ms, System: 0.1 ms]
  Range (min … max):     1.9 ms …   2.8 ms    924 runs

Looking at the traces:

Before:

After (there are no GC collections in this trace)

1MB seems like a good start, we can always bump it higher or adjust after this, V8's nursery size before GC kicks in seems to be between 1-8MB,

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.51%. Comparing base (6ddc2b4) to head (438838e).
Report is 202 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3908      +/-   ##
==========================================
+ Coverage   47.24%   51.51%   +4.26%     
==========================================
  Files         476      467       -9     
  Lines       46892    44724    -2168     
==========================================
+ Hits        22154    23039     +885     
+ Misses      24738    21685    -3053     

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[nekevss]

Small comment, non-blocking though.