Initializing LineHeights is slow when having many custom line heights

[alexdima]

• open large.ts
• configure:

 "editor.tokenColorCustomizations": {
        "textMateRules": [
            {
                "scope": "comment.line.double-slash.ts",
                "settings": {
                    "fontSize": 1.2,
                }
            }
        ]
    },

• switch in a tab between large.ts and another file

• 🐛 switching to large.ts feels janky.

• this is especially janky if there are let's say 10K cursors.