fix(tracemetrics): Bump metric buffer to 1k

[k-fish]

Summary

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

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	9,025	-	9,643	-6%
GET With Sentry	1,383	15%	1,422	-3%
GET With Sentry (error only)	6,151	68%	6,216	-1%
POST Baseline	1,213	-	1,219	-0%
POST With Sentry	524	43%	561	-7%
POST With Sentry (error only)	1,067	88%	1,071	-0%
MYSQL Baseline	3,291	-	3,392	-3%
MYSQL With Sentry	477	14%	477	-
MYSQL With Sentry (error only)	2,713	82%	2,748	-1%

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