If a calculation was simplified down to a single numeric node, then most
of the time we can instead return a regular StyleValue, for example
`calc(2px + 3px)` would be simplified down to a `5px` LengthStyleValue.
This means that parse_calculated_value() can't return a
CalculatedStyleValue directly, and its callers all have to handle
non-calculated values as well as calculated ones.
This simplification is reflected in the new test results. Serialization
is not yet correct in all cases but we're closer than we were. :^)
Ignoring the fact that we should serialize a simplified form of calc()
expressions, the following are wrong:
- grid-auto-columns
- grid-auto-rows
- grid-template-columns
- grid-template-rows
- transform-origin
Generated in part with this python script (though I've since iterated on
the output repeatedly so it's quite different):
```py
import json
properties_file = open("./Userland/Libraries/LibWeb/CSS/Properties.json")
properties = json.load(properties_file)
for (key, value) in properties.items():
if not 'valid-types' in value:
continue
if 'longhands' in value:
continue
valid_types = value['valid-types']
for type_string in valid_types:
name, *suffix = type_string.split(None, 1)
match name:
case 'integer' | 'number':
print(f'{key}: calc(2 * var(--n));')
case 'angle':
print(f'{key}: calc(2deg * var(--n));')
case 'flex':
print(f'{key}: calc(2fr * var(--n));')
case 'frequency':
print(f'{key}: calc(2hz * var(--n));')
case 'length':
print(f'{key}: calc(2px * var(--n));')
case 'percentage':
print(f'{key}: calc(2% * var(--n));')
case 'resolution':
print(f'{key}: calc(2x * var(--n));')
case 'time':
print(f'{key}: calc(2s * var(--n));')
```
