[frontend] fix RUM instrumentation by updating deprecated properties

RUM instrumentation is broken, since we are relying on latest
version from CDN and v1 was released with breaking changes.

Updated the following configs based on
https://github.com/signalfx/splunk-otel-js-web/blob/main/CHANGELOG.md#100

 - beaconUrl -> beaconEndpoint
 - app -> applicationName
 - environment -> deploymentEnvironment
 - rumAuth -> rumAccessToken

Author: mvirgil

src/frontend/templates/header.html

@@ -16,7 +16,7 @@
     <link rel='shortcut icon' type='image/x-icon' href='/static/favicon.ico' />
     {{- if and $.rum_realm $.rum_auth }}
     <script src="https://cdn.signalfx.com/o11y-gdi-rum/latest/splunk-otel-web.js" type="text/javascript"></script>
-    <script>window.SplunkRum && window.SplunkRum.init({beaconUrl: "https://rum-ingest.{{ $.rum_realm }}.signalfx.com/v1/rum", rumAuth: "{{ $.rum_auth }}"{{ if $.rum_app_name }}, app: "{{ $.rum_app_name }}"{{ end }}{{ if $.rum_environment }}, environment: "{{ $.rum_environment }}"{{ end }}{{ if $.rum_debug }}, debug: "true"{{ end }}});</script>
+    <script>window.SplunkRum && window.SplunkRum.init({beaconEndpoint: "https://rum-ingest.{{ $.rum_realm }}.signalfx.com/v1/rum", rumAccessToken: "{{ $.rum_auth }}"{{ if $.rum_app_name }}, applicationName: "{{ $.rum_app_name }}"{{ end }}{{ if $.rum_environment }}, deploymentEnvironment: "{{ $.rum_environment }}"{{ end }}{{ if $.rum_debug }}, debug: "true"{{ end }}});</script>
     {{- end }}
 </head>