Refactor hosted key handling. Add optimistic handling of throttling for custom throttle rules.

Author: Theodore Li

apps/sim/lib/core/hosted-key-throttler/index.ts

@@ -0,0 +1,17 @@
+export {
+  getHostedKeyRateLimiter,
+  HostedKeyRateLimiter,
+  resetHostedKeyRateLimiter,
+} from './rate-limiter'
+export {
+  DEFAULT_BURST_MULTIPLIER,
+  DEFAULT_WINDOW_MS,
+  toTokenBucketConfig,
+  type AcquireKeyResult,
+  type CustomRateLimit,
+  type HostedKeyRateLimitConfig,
+  type HostedKeyRateLimitMode,
+  type PerRequestRateLimit,
+  type RateLimitDimension,
+  type ReportUsageResult,
+} from './types'