feat(http-add-on): allow override of specific component image tag

[ilia-medvedev]

Add possibility to override specific component tag for http-add-on

closes #759

Checklist

• [x] I have verified that my change is according to the deprecations & breaking changes policy
• [x] Commits are signed with Developer Certificate of Origin (DCO - learn more)
• [x] README is updated with new configuration values (if applicable) learn more
• [x] A PR is opened to update KEDA core (repo) (if applicable, ie. when deployment manifests are modified)

Fixes #