chore: add scaletest convenience script (#7819)

- Adds a convenience script `scaletest.sh` to automate process of running scale tests
- Enables pprof endpoint by default, and captures pprof traces before tearing down infra.
- Improves idempotency of coder_init.sh
- Removes the promtest.Float64 invocations in workspacetraffic runner, these metrics will be in prometheus.
- Increases default workspace traffic output to 40KB/s/workspace.

scaletest/lib/coder_shim.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# This is a shim for easily executing Coder commands against a loadtest cluster
+# without having to overwrite your own session/URL
+PROJECT_ROOT="$(git rev-parse --show-toplevel)"
+# shellcheck source=scripts/lib.sh
+source "${PROJECT_ROOT}/scripts/lib.sh"
+CONFIG_DIR="${PROJECT_ROOT}/scaletest/.coderv2"
+CODER_BIN="${CONFIG_DIR}/coder"
+DRY_RUN="${DRY_RUN:-0}"
+maybedryrun "$DRY_RUN" exec "${CODER_BIN}" --global-config "${CONFIG_DIR}" "$@"