[MERGE #5032 @sethbrenith] Share type handler for strict-mode arguments object
Merge pull request #5032 from sethbrenith:user/sethb/strict-args
The Preact test in Speedometer is spending around 3% of its script time in LoadHeapArguments, which is currently slower for strict mode than sloppy mode because we don't share types. This change updates CreateHeapArguments to use a single shared type for all strict-mode `arguments` objects, which improves the following microbenchmark by about 34%. Overall Preact improvement is much more modest; I'd guess 0.3% based on trace data comparison.
```javascript
function arg() {
"use strict";
return Array.prototype.slice.call(arguments)[0];
}
const start = Date.now();
for (let i = 0; i < 1e6; ++i) {
arg(i);
}
print(Date.now() - start);
```
