[FEATURE] Kvssink deliver-images with putEventMetadata

[niyatim23]

Issue #, if available:

Description of changes:

• Introduced a new prop / attribute in kvssink which allows enabling / disabling image-generation
• Surfaced a public API- putEventMetadata from the C layer to the CPP layer

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Issue #, if available:

What was changed?

• Introduced a new prop / attribute in kvssink which allows enabling / disabling image-generation

Why was it changed?

• To maintain feature parity between producer c, cpp and kvssink

How was it changed?

• Surfaced a public API- putEventMetadata from the C layer to the CPP layer.
• It is invoked from gst_kvs_sink_handle_buffer for every key frame if the generate_images bool is set

What testing was done for the changes? Tested the following locally:

• Tested that the image tags were added to the video with mkvinfo when generate-images was set to TRUE
• Tested that setting generate-images to FALSE doesn't generate image tags in the video

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.