lib: nb: call child destroy CBs when YANG container is deleted

[choppsv1]

Previously the code was only calling the child destroy callbacks if the target deleted node was a non-presence container. We now add a flag to the callback structure to instruct northbound to perform the rescursive delete.

• Fix wrong relative path lookup in keychain destroy callback

[idryzhov]

While it should work and convenient for the developers, it can be very suboptimal. For example, you have a staticd frr-rt:control-plane-protocol instance with 100k routes, and you delete this instance. Current code handles it in a single operation, which I guess is much faster than executing 100k individual callbacks (actually much much more because there are dozens of individual leafs in each static route and each will be deleted individually).

I would at least test the time difference for this scenario as it can be really huge. Maybe it makes sense to make recursive deletion optional, to use in cases where thousands of child nodes are not expected.

[idryzhov]

Left a comment above that should be at least discussed before merging this.

Looks fine with an optional flag. Not approving yet because the PR is in draft state.

[Jafaral]

@Mergifyio backport dev/10.3 stable/10.2

[mergify]

backport dev/10.3 stable/10.2

✅ Backports have been created

• #18191 lib: nb: call child destroy CBs when YANG container is deleted (backport #18082) has been created for branch dev/10.3
• #18192 lib: nb: call child destroy CBs when YANG container is deleted (backport #18082) has been created for branch stable/10.2