Add dynamic CSS "empty" disclaimer to all datagrids

[niklasmohrin]

Closes #2662

I made two separate commits, the first has the meaningful changes and the second fixes the indentation.

[janno42]

I can see the 🎆

[niklasmohrin]

Waiting for #2587 to spare them the rebase

[niklasmohrin]

I think we are running into a firefox bug on the questionnaire index. The first time (per tab) that I filter for something, if it matches nothing (i.e. you have to enter something like adljaladljad right away without a table update from a prefix), the disclaimer does not show up. The disclaimer shows up if:

1. this is not the first time that the table contents change
2. the table is initially empty (for example reload page with something in search box)

It does work again if you remove the filter, switch to another questionnaire tab, and enter alkjhdf again. Very strange. In chromium everything works as expected

[niklasmohrin]

Oh, I can also get it to break in other places. Semester view, enter something that doesn't match anything (evaluation or course list, doesn't matter). Reload page. Empty table, no disclaimer. Funnily enough, this is exactly the opposite of when it breaks on the questionnaire page

[niklasmohrin]

Probably firefox is tripping up with our table contents remove and append here

EvaP/evap/static/ts/src/datagrid.ts

Lines 211 to 216 in 8807428

	protected renderToDOM() {
	[...this.container.children].map(element => element as HTMLElement).forEach(element => element.remove());
	const elements = this.rows.filter(row => row.isDisplayed).map(row => row.element);
	this.container.append(...elements);
	this.saveStateToStorage();
	}

and fails to apply CSS rules?

[fekoch]

Oh, I can also get it to break in other places. Semester view, enter something that doesn't match anything (evaluation or course list, doesn't matter). Reload page. Empty table, no disclaimer. Funnily enough, this is exactly the opposite of when it breaks on the questionnaire page

Interesting, I can reproduce it, but not consistently. When reloading multiple times, the notice sometimes shows and sometimes is missing.

Additionally, I can not reproduce it, if I have my devtools open 🙃 ...

[fekoch]

I opened a ticket at bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=2035307