maint: add setup for load testing (#143)

## Which problem is this PR solving?

easy setup for load testing

## Short description of the changes

- Add [echoserver](https://hub.docker.com/r/ealen/echo-server) as
Kubernetes deployment to use with Locustfile

## How to verify that this has the expected result

Follow instructions in the loadtest doc 


![loadtestinhoneycomb](https://github.com/honeycombio/honeycomb-ebpf-agent/assets/29520003/468b2113-3f6f-4830-a216-bbd802e79aaf)

---------

Co-authored-by: Vera Reynolds <vreynolds@users.noreply.github.com>
Co-authored-by: Mike Goldsmith <goldsmith.mike@gmail.com>

smoke-tests/echoserver.yaml

@@ -0,0 +1,43 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: echoserver
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: echoserver
+  namespace: echoserver
+spec:
+  replicas: 5
+  selector:
+    matchLabels:
+      app: echoserver
+  template:
+    metadata:
+      labels:
+        app: echoserver
+    spec:
+      containers:
+        - image: ealen/echo-server:latest
+          imagePullPolicy: IfNotPresent
+          name: echoserver
+          ports:
+            - containerPort: 80
+          env:
+            - name: PORT
+              value: "80"
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: echoserver
+  namespace: echoserver
+spec:
+  selector:
+    app: echoserver
+  ports:
+    - name: http
+      port: 80
+      targetPort: 80
+  type: LoadBalancers

smoke-tests/loadtest.md

@@ -0,0 +1,30 @@
+# Load Testing
+
+1. Deploy echo server
+
+    ```shell
+    k apply -f echoserver.yaml
+    ```
+
+2. Build & deploy agent
+
+    ```shell
+    make docker-build
+    HONEYCOMB_API_KEY=abc make apply-ebpf-agent
+    ```
+
+3. Start load test
+
+    ```shell
+    locust
+    ```
+
+4. Run load test with 5-6k concurrent users at 100 users/s ramp up. It's not always going to get messed up, but when it does it will usually happen within a minute or two of starting the load test.
+
+5. Watch the data in Honeycomb. You can tell when the matching starts to break down. You can see it in Honeycomb on a duration heatmap (it starts to first get much larger than average, and then goes negative).
+
+6. Tear down echo server
+
+    ```shell
+    k delete -f echoserver.yaml
+    ```

smoke-tests/locustfile.py

@@ -0,0 +1,12 @@
+import time, random
+from locust import HttpUser, task, between
+
+
+class QuickstartUser(HttpUser):
+    host = "http://localhost:80"
+    wait_time = between(1, 2)
+
+    @task
+    def hello_greeting(self):
+        i = random.randrange(1, 10)
+        self.client.get("/?echo_body=" + str(i))