(feat/SEC-1010): Add SAST scanning using semgrep

[saisatishkarra]

Perform SAST scanning in a non-blocking fashion (configurable) by default using shared kong action maintained by sec team.

The Shared Action Doc can be found here.

Event triggers:

• PR without dependabot[bot] as an actor only on diff / changed files that match default semgrep config
• Push to develop / release/* branches
• Any workflow dispatch

Additional overrides:

Output:

• Uploads findings to the Security tab (uses GH CodeQL and Advanced security tab) for a public repo
• Generates a workflow artifact/console log output of the results

Other notes:

Closes INS-3504 (linear)

[CLAassistant]

All committers have signed the CLA.

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[saisatishkarra]

cc: @vs-kong @filfreire for review

[filfreire]

LGTM