[Release] logzio-k8s-telemetry align to new global structure

[8naama]

Description

• Change Logz.io secret values to global to prevent duplicate values in the parent chart
  • secrets.MetricsToken >> global.logzioMetricsToken
  • secrets.TracesToken >> global.logzioTracesToken
  • secrets.SpmToken >> global.logzioSpmToken
  • secrets.k8sObjectsLogsToken >> global.logzioLogsToken
  • secrets.env_id >> global.env_id
  • secrets.LogzioRegion >> global.logzioRegion
  • secrets.CustomTracingEndpoint >> global.customTracesEndpoint
  • Deprecate secrets.p8s_logzio_name and secrets.ListenerHost
    • Add support for global.customMetricsEndpoint to substitute the custom endpoint ability that was supported with secrets.ListenerHost
• Update readme
• Align tests

Note: in contrast to the changes in other charts, I didn't make the below changes due to logzio-k8s-telemetry being replaced with logzio-metrics-collector in the near future:

1. Move changelog from README.md to CHANGELOG.md
2. Rename K8s secret resource configuration secrets >> secret

What type of PR is this?

(check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 🧑‍💻 Code Refactor
• 🔥 Performance Improvements
• ✅ Test
• 🤖 Build / CI
• ⏩ Revert

Added tests?

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help from somebody