fix(Tooltip): dismiss tooltip and popover on Escape key (WCAG 1.4.13)

[mrholek]

Ports the vanilla tooltip Escape-key dismissal (coreui/coreui#1126, coreui-pro#609) to the React CTooltip and CPopover (a11y — WCAG 1.4.13 "Content on Hover or Focus"): a hover/focus tooltip or popover could not be dismissed from the keyboard.

• While shown (_visible), a keydown listener is attached to document in the capture phase; on Escape it preventDefault() + stopPropagation() and calls handleHide(). Removed automatically when _visible flips false (effect cleanup on [_visible]).
• Capture phase = the tooltip/popover dismisses before an ancestor dialog's own Escape handler (nested dismissal).
• Applied to both CTooltip and CPopover (separate components in React).
• Tests: dismiss-on-Escape + non-Escape-ignored for each component. Docs updated (tooltip Usage, popover Dismiss section).