fix(tracemetrics): Bump metric buffer size to 1k (#5031)

We've been noticing some discards from clients for likely buffer reason. Metrics were
initially set to 100 to match logs but the size limit for a metric in relay is ~1000x less (~1-2kb at the moment) so the memory pressure should be fine (it'd cap in the single digit megabyte range).

Author: k-fish

sentry_sdk/_metrics_batcher.py

@@ -12,7 +12,7 @@
 
 
 class MetricsBatcher:
-    MAX_METRICS_BEFORE_FLUSH = 100
+    MAX_METRICS_BEFORE_FLUSH = 1000
     FLUSH_WAIT_TIME = 5.0
 
     def __init__(