Added support for custom icons in various editor inputs

[benibenj]

This PR introduces the ability to use codicons in various editor inputs. The changes include modifications to the editor input classes to accept a ThemeIcon object, which can be used to set a custom icon.

#199965
#200147

[bpasero]

Great small change, here are more editors to consider adopting:

• WorkspaceTrustEditorInput
• WalkThroughInput
• GettingStartedInput
• TerminalEditorInput
• RuntimeExtensionsInput
• DissassemblyViewInput
• ChatEditorInput

[Tyriar]

If you do TerminalEditorInput, note that the icon (codicon or uri) and its color is currently dynamic (driven via CSS):

vscode/src/vs/workbench/contrib/terminal/browser/terminalEditorInput.ts

Lines 194 to 211 in faacc5f

	override getLabelExtraClasses(): string[] {
	if (!this._terminalInstance) {
	return [];
	}
	const extraClasses: string[] = ['terminal-tab'];
	const colorClass = getColorClass(this._terminalInstance);
	if (colorClass) {
	extraClasses.push(colorClass);
	}
	const uriClasses = getUriClasses(this._terminalInstance, this._themeService.getColorTheme().type);
	if (uriClasses) {
	extraClasses.push(...uriClasses);
	}
	if (ThemeIcon.isThemeIcon(this._terminalInstance.icon)) {
	extraClasses.push(`codicon-${this._terminalInstance.icon.id}`);
	}
	return extraClasses;
	}

[benibenj]

Great small change, here are more editors to consider adopting:

• WorkspaceTrustEditorInput
• WalkThroughInput
• GettingStartedInput
• TerminalEditorInput
• RuntimeExtensionsInput
• DissassemblyViewInput
• ChatEditorInput

Added support for all EditorInputs except WalkThroughInput and GettingStartedInput as these set an svg for which we do not have a codicon.

[benibenj]

I only partially supported TerminalEditorInput as I am not sure how to support URI icons. Also, I don't support changing the colour of the icon provided by an EditorInput yet which I am planning on looking into in a follow up PR.

[Tyriar]

If you don't do color yet we should move the terminal back to the old system until then as it would be a regression

[benibenj]

I will be looking into icon theme colours tomorrow. For the TerminalEditorInput, the icon colours should still be working after this PR as the colour classes are still being added to the extra classes as before. If it does not work then it's due to changing the CSS classes which are added to the div. In that case I'll just need to make a small adaption.