[Calendar][PrimeIcons] - Chevrons lack tabindex which interrupts tabbing, empty href

[Mysame]

primeng/src/app/components/calendar/calendar.ts

Lines 45 to 50 in 189a80d

	<a class="ui-datepicker-prev ui-corner-all" href="#" (click)="navBackward($event)" *ngIf="i === 0">
	<span class="pi pi-chevron-left"></span>
	</a>
	<a class="ui-datepicker-next ui-corner-all" href="#" (click)="navForward($event)" *ngIf="numberOfMonths === 1 ? true : (i === numberOfMonths -1)">
	<span class="pi pi-chevron-right"></span>
	</a>

Chevrons get "tabbed" to, which makes tabbing out of a Calendar a 2-tab process.
Replicatable on https://www.primefaces.org/primeng/#/calendar , enter a Calendar, press "tab", you can breakpoint and/or notice the left chevron colouring blue.

Fix: Give the <a> a tabindex of -1

Additionally, empty href's should be replaced by appropriate cursor styling

[anfeloaiza]

+1

[Mysame]

@cagataycivici I regret to inform that this is not fixed by #6760 .

A distinction should be made between what requires tabindex="0" and tabindex="-1".
-1 will be ignored by browser.