Pushing cloud-init log to the KVP (#529)

Push the cloud-init.log file (Up to 500KB at once) to the KVP before reporting ready to the Azure platform.
Based on the analysis done on a large sample of cloud-init.log files, Here's the statistics collected on the log file size:
P50 	P90 	P95 	P99 	P99.9 	P99.99
137K 	423K 	537K 	3.5MB 	6MB 	16MB

This change limits the size of cloud-init.log file data that gets dumped to KVP to 500KB. So for ~95% of the cases, the whole log file will be dumped and for the remaining ~5%, we will get the last 500KB of the cloud-init.log file.
To asses the performance of the 500KB limit, 250 VM were deployed with a 500KB cloud-init.log file and the time taken to compress, encode and dump the entries to KVP was measured. Here's the time in milliseconds percentiles:
P50 	P99 	P999
75.705 	232.701 	1169.636

Another 250 VMs were deployed with this logic dumping their normal cloud-init.log file to KVP, the same timing was measured as above. Here's the time in milliseconds percentiles:
P50 	P99 	P999
1.88 	5.277 	6.992

Added excluded_handlers to the report_event function to be able to opt-out from reporting the events of the compressed cloud-init.log file to the cloud-init.log file.

The KVP break_down logic had a bug, where it will reuse the same key for all the split chunks of KVP which results in overwriting the split KVPs by the last one when consumed by Hyper-V. I added the split chunk index as a differentiator to the KVP key.

The Hyper-V consumes the KVPs from the KVP file as chunks whose key is 512KB and value is 2048KB but the Azure platform expects the value to be 1024KB, thus I introduced the Azure value limit.

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