feat: add message gateway source code

[bsalsingh]

Description

• message gateway module with slack adapter implementation
• bump the l0-agent version to v1.1 in helm chart
• add c1,c2 and c3 charts in docs

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Type of Change

• New feature (non-breaking change which adds functionality)
• Documentation update

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Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have added comments, especially in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules