Feature: tier XI compatibility

Prepares BlitzKit for tier XI tanks ahead of their release. Tier X was hardcoded as the maximum in the tank search filters, the guesser and the tech tree, and had no roman numeral beyond X.

- Added `XI` to `TIER_ROMAN_NUMERALS`
- Added an awaitable tier list derived from the highest tier in the tank definitions, so nothing changes until tier XI tanks exist
- Used it for the tank search tier filters and the guesser tier picker and defaults
- Made the tech tree check for successors instead of assuming tier X is the last tier

Fixes #302

packages/core/src/blitzkit/tankDefinitions/constants.ts

@@ -54,6 +54,7 @@ export const TIER_ROMAN_NUMERALS: Record<number, string> = {
   8: "VIII",
   9: "IX",
   10: "X",
+  11: "XI",
 };
 
 export const flags: Record<string, string> = {