Add [nzTooltipContext] and provide it to the embedded view

[ppacher]

What problem does this feature solve?

I'd like to re-use a <ng-template #templateRef> between multiple instances of [nzTooltipTitle] but need to have access to context variables like those produced by *ngFor. Right now I'm forced to created a <ng-template> in each ngFor iteration. This would also allow the reuse of a template accross different *ngFor instances.

The same applies for related APIs like nz-popover.

What does the proposed API look like?

<h1>Events Today</h1>
<ul>
    <li *ngFor="let event of events.today" nz-tooltip [nzTooltipTitle]="tooltipTemplate" [nzTooltipContext]="{$implicit: event}">
       {{ event.summary }}
    </li>
</ul>

<h1>Events Tomorrow</h1>
<ul>
    <li *ngFor="let event of events.tomorrow" nz-tooltip [nzTooltipTitle]="tooltipTemplate" [nzTooltipContext]="{$implicit: event}">
       {{ event.summary }}
    </li>
</ul>

<ng-template #tooltipTemplate let-event>
    <!-- imagine some more complicated or layouted content -->
    <b>{{ event.description }}</b>
</ng-template>
```<!-- generated by ng-zorro-issue-helper. DO NOT REMOVE -->

[ppacher]

Just after creating this issue I found #4706 which basically requests a similar solution for nz-dropdown.

[wzhudev]

Will do (sorry I have been occupied by other things).