Investigate moving away from the styler pattern

[alexdima]

Having more styling be done via CSS would reduce the amount of JS code we need to ship and run. We should investigate if it is possible to achieve the same composition as we do today in JS, by using CSS variables. We should also check that this doesn't cause any performance problems and that it is idiomatic CSS

/* in base widget CSS */
.monaco-inputbox {
    --monaco-inputbox-foreground: #CCCCCC;
}
.monaco-inputbox {
    position: relative;
    display: block;
    padding: 0;
    box-sizing: border-box;
    border-radius: 2px;
    /* Customizable */
    font-size: inherit;
    color: var(--monaco-inputbox-foreground)
}

/* in widget user CSS */
.findWidget .monaco-inputbox {
    --monaco-inputbox-foreground: var(--vscode-find-widget-input);
}

[aeschli]

Half of the stylers have been converted, still more to do.

[aeschli]

All stylers replaced

[aeschli]

Verify in source that there is no more styler.ts