fix(ButtonIcon): drop tooltip defaults that shadow global BTooltip config

[lschim]

Problem

ButtonIcon declares hardcoded defaults for two tooltip props:

tooltipPlacement: 'top',
tooltipDelay: () => ({ show: 0, hide: 0 }),

It then forwards them unconditionally to its <b-tooltip>. bootstrap-vue-next resolves a globally configured default only when a prop is absent from the vnode (propIsDefined in useDefaults), so a concrete value passed here permanently shadows it.

The practical effect in a consuming app: configuring tooltips globally is a no-op for every button.

createBootstrap({ components: { BTooltip: { delay: { show: 3000, hide: 0 } } } })

Every ButtonIcon keeps { show: 0, hide: 0 }. Since ButtonIcon is the base button of downstream applications, this covers most tooltips in them. We hit this in datashare-client while trying to set an application-wide hover delay.

Fix

Remove both defaults. BTooltip then applies its own, and a global default wins when one is configured. Callers passing tooltip-placement or tooltip-delay explicitly are unaffected.

Behaviour

tooltipPlacement is strictly neutral: BPopover already defaults placement to 'top'.

tooltipDelay is neutral for the main button tooltip (BTooltip declares delay: 0), with one intentional exception. The iconLeftLabel / iconRightLabel tooltips use the v-b-tooltip directive, which renders a BPopover directly, and BPopover defaults delay to { show: 100, hide: 300 }. Measured on the timer useShowHide actually schedules:

	show delay on hover
before	0 ms
after	100 ms

100 ms is bootstrap-vue-next's intended default and is imperceptible, but it is a real change and can now be overridden globally, which was the point.

Tests

New tests/unit/components/Button/ButtonIconTooltip.spec.ts asserts the props reaching the tooltip vnode, plus one integration test proving a globally configured BTooltip delay now reaches the rendered BPopover. Three of the five tests fail without the change.

Full suite: 856 tests passing, lint clean, build:lib clean.