Run test_packet_buffer_writer through miri

ci/test-miri.sh

@@ -7,8 +7,8 @@ source ci/rust-version.sh nightly
 
 # miri is very slow; so only run very few of selective tests!
 _ cargo "+${rust_nightly}" miri test -p solana-program -- hash:: account_info::
-
 _ cargo "+${rust_nightly}" miri test -p solana-unified-scheduler-logic
+_ cargo "+${rust_nightly}" miri test -p solana-packet -- test_packet_buffer_writer
 
 # run intentionally-#[ignored] ub triggering tests for each to make sure they fail
 (! _ cargo "+${rust_nightly}" miri test -p solana-unified-scheduler-logic -- \