LibWeb: Bring CSS line-height closer to other engines

This patch makes a few changes to the way we calculate line-height:

- `line-height: normal` is now resolved using metrics from the used
  font (specifically, round(A + D + lineGap)).

- `line-height: calc(...)` is now resolved at style compute time.

- `line-height` values are now absolutized at style compute time.

As a consequence of the above, we no longer need to walk the DOM
ancestor chain looking for line-heights during style computation.
Instead, values are inherited, resolved and absolutized locally.

This is not only much faster, but also makes our line-height metrics
match those of other engines like Gecko and Blink.

Tests/LibWeb/Text/expected/HTML/HTMLInputElement-valueAsNumber.txt

@@ -43,4 +43,4 @@ file threw exception: InvalidStateError: valueAsNumber: Invalid input type used
 submit threw exception: InvalidStateError: valueAsNumber: Invalid input type used
 image threw exception: InvalidStateError: valueAsNumber: Invalid input type used
 reset threw exception: InvalidStateError: valueAsNumber: Invalid input type used
-button threw exception: InvalidStateError: valueAsNumber: Invalid input type used
+button threw exception: InvalidStateError: valueAsNumber: Invalid input type used

Tests/LibWeb/Text/expected/HTML/StructuredClone-object-primitives.txt

@@ -14,4 +14,4 @@ true
 1
 true
 [object ArrayBuffer]
-ERROR: DataCloneError: Cannot serialize Symbol
+ERROR: DataCloneError: Cannot serialize Symbol

Tests/LibWeb/Text/expected/HTML/StructuredClone-primitives.txt

@@ -5,4 +5,4 @@ false
 123
 123.456
 9007199254740991
-This is a string
+This is a string

Tests/LibWeb/Text/expected/HTML/Window-named-properties-elements.txt

@@ -3,4 +3,4 @@ true
 true
 true
 true
-true
+true

Tests/LibWeb/Text/expected/HTML/Window-named-properties-iframe.txt

@@ -1,2 +1,2 @@
    true
-true
+true

Tests/LibWeb/Text/expected/HTML/Window-prototype.txt

@@ -3,4 +3,4 @@
 [object WindowProperties]
 [object EventTarget]
 [object Object]
-null
+null