roachtest: add scaffolding for new kv rangefeed tests

This adds a new kv-rangefeed test suite. These roachtests are aimed at
understanding the behavior of the server-side rangefeed components. To
achieve this, our plan is:

1) Use a sink with a known capacity such that we can differentiate
   between the "correctly provisioned" and "under-provisioned" sink
   cases.

2) Assert that any sink that is correctly provisioned eventually catches up.

3) Assert that regardless of sink provisioning, we never impact p99
foreground SQL latency.

This adds a small example test along with most of the scaffolding needed
to add more tests in future PRs.

Epic #CRDB-55203
Release note: None

Co-authored-by: Wenyi Hu <wenyi@cockroachlabs.com>

Author: stevendanna

pkg/cmd/roachtest/tests/BUILD.bazel

@@ -104,6 +104,7 @@ go_library(
         "kerberos_connection_stress.go",
         "knex.go",
         "kv.go",
+        "kv_rangefeed.go",
         "kvbench.go",
         "large_kv.go",
         "large_schema_backup_restore.go",
@@ -375,6 +376,7 @@ go_test(
         "blocklist_test.go",
         "cdc_helper_test.go",
         "drt_test.go",
+        "kv_rangefeed_test.go",
         "nodejs_helpers_test.go",
         "query_comparison_util_test.go",
         "restore_test.go",