fix(calendar): clean up d3-tip tooltips

[sadpandajoe]

fix(calendar): clean up d3-tip tooltips

SUMMARY

• Adds a Calendar Heatmap-specific d3-tip class so tooltip DOM nodes can be cleaned up without affecting other charts.
• Removes stale Calendar Heatmap tooltips before redraw and when the React wrapper unmounts.
• Destroys the vendor Calendar Heatmap cell and legend d3-tip instances when the calendar is destroyed.

Fixes #41583

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Not applicable; tooltip cleanup is covered by a DOM-level regression test.

TESTING INSTRUCTIONS

• cd superset-frontend && NODE_ENV=test NODE_OPTIONS='--max-old-space-size=8192' npx jest --runInBand --silent plugins/legacy-plugin-chart-calendar/test/tooltip.test.ts plugins/legacy-plugin-chart-calendar/test/utils.test.ts
• cd superset-frontend && npx oxlint --config oxlint.json plugins/legacy-plugin-chart-calendar/src/Calendar.ts plugins/legacy-plugin-chart-calendar/src/ReactCalendar.tsx plugins/legacy-plugin-chart-calendar/src/tooltip.ts plugins/legacy-plugin-chart-calendar/src/vendor/cal-heatmap.ts plugins/legacy-plugin-chart-calendar/test/tooltip.test.ts

ADDITIONAL INFORMATION

• Has associated issue: Tooltips in the calendar heat map charts can remain in DOM even when navigating away from a dashboard #41583
• Required feature flags: none
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)