Refactor load testing scripts to support Bash and PowerShell

- Updated README.md to reflect changes in load testing commands and added usage examples for Bash scripts.
- Converted PowerShell load testing scripts to Bash equivalents for better cross-platform compatibility.
- Added new Bash scripts: run-loadtests.sh, summarize-artillery.sh, and summarize-k6.sh to mirror existing PowerShell functionality.
- Updated admin-api.js and ws-chat.yml for consistency and improved performance metrics reporting.
- Enhanced error handling and output formatting in summary scripts for better readability.

scripts/loadtest/ws-chat.yml

@@ -1,28 +1,28 @@
-config:
-  target: "{{ $processEnvironment.WS_URL }}"
-  phases:
-    - duration: 60
-      arrivalRate: 10
-      name: warmup-10
-    - duration: 120
-      arrivalRate: 100
-      name: sustain-100
-    - duration: 180
-      arrivalRate: 500
-      name: sustain-500
-    - duration: 240
-      arrivalRate: 1000
-      name: sustain-1000
-  engines:
-    ws: {}
-scenarios:
-  - engine: ws
-    name: chat-presence-and-send
-    flow:
-      - think: 1
-      - send:
-          text: '{"type":"ping","text":"loadtest"}'
-      - think: 1
-      - send:
-          text: '{"type":"ping","text":"loadtest-2"}'
-      - think: 1
+config:
+  target: "{{ $processEnvironment.WS_URL }}"
+  phases:
+    - duration: 60
+      arrivalRate: 10
+      name: warmup-10
+    - duration: 120
+      arrivalRate: 100
+      name: sustain-100
+    - duration: 180
+      arrivalRate: 500
+      name: sustain-500
+    - duration: 240
+      arrivalRate: 1000
+      name: sustain-1000
+  engines:
+    ws: {}
+scenarios:
+  - engine: ws
+    name: chat-presence-and-send
+    flow:
+      - think: 1
+      - send:
+          text: '{"type":"ping","text":"loadtest"}'
+      - think: 1
+      - send:
+          text: '{"type":"ping","text":"loadtest-2"}'
+      - think: 1