ref(ourlogs): Add option to control breadcrumb extraction (#84212)

### Summary
To avoid rollout issues when turning on s4s and other environments for
the first time, this option will control the rate at which logs are
extracted from breadcrumbs.

src/sentry/options/defaults.py

@@ -513,6 +513,15 @@
     flags=FLAG_ALLOW_EMPTY | FLAG_PRIORITIZE_DISK | FLAG_AUTOMATOR_MODIFIABLE,
 )
 
+# Extract logs from breadcrumbs only for a random fraction of sent breadcrumbs.
+#
+# NOTE: Any value below 1.0 will break the product. Do not override in production.
+register(
+    "relay.ourlogs-breadcrumb-extraction.sample-rate",
+    default=0.0,
+    flags=FLAG_AUTOMATOR_MODIFIABLE,
+)
+
 
 # Extract spans only from a random fraction of transactions.
 #

src/sentry/relay/globalconfig.py

@@ -21,6 +21,7 @@
     "relay.metric-bucket-set-encodings",
     "relay.metric-bucket-distribution-encodings",
     "relay.metric-stats.rollout-rate",
+    "relay.ourlogs-breadcrumb-extraction.sample-rate",
     "relay.span-extraction.sample-rate",
     "relay.span-normalization.allowed_hosts",
     "relay.drop-transaction-attachments",