Bug 1843499 - Part 3: Add exception stack to finally. r=iain

Bug 1843499 - Part 3: Add exception stack to finally. r=iain

Similar to the last part 2, re-throw the original stack trace in `finally`
blocks. This is implemented by changing `finally` blocks to push the exception
stack onto the value stack.

Using test262 assertions:
```
try {
  assert.throws(TypeError, () => {});  // This is line 2.
} finally {
  assert.sameValue(0, 0);  // This is line 4. (End of finally block)
}
```

Before:
```
/tmp/a.js:4:10 uncaught exception: Test262Error: Expected a TypeError to be thrown but no exception was thrown at all
Stack:
  @/tmp/a.js:4:10
```

Now:
```
/tmp/test262-assert.js:104:9 uncaught exception: Test262Error: Expected a TypeError to be thrown but no exception was thrown at all
Stack:
  assert.throws@/tmp/test262-assert.js:104:9
  @/tmp/a.js:2:10
```

Differential Revision: https://phabricator.services.mozilla.com/D183564