[Release] fluentd align to new global structure

[8naama]

Description

• Change secret values to global and align the names to prevent duplicate values in the parent chart
  • secrets.logzioShippingToken >> global.logzioLogsToken
  • secrets.logzioListener >> global.logzioRegion
  • secrets.customEndpoint >> global.customLogsEndpoint
  • env_id >> global.env_id
• K8s secret resource configuration has been renamed secrets >> secret
  • secretName >> secret.name
• Move changelog from README.md >> CHANGELOG.md
• Update readme
• Align tests

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

[ralongit]

💯