feat: introduce exp. backoff for polling

[sudo-suhas]

• Introduce active poll percent configuration to determine the percentage of workers that should actively poll as per the specified poll interval irrespective of whether a job was found or not.
• For a non-active poll worker, when no job is found, use exponential backoff to determine the poll delay for next attempt.
• Fix bug in exponential backoff calculation where it would return 0 as the backoff duration for high attempt number such as 70.
• Add instance name to otelsql instrumentation and use nrpgx driver for default PostgreSQL client (was missed).

[coveralls]

Pull Request Test Coverage Report for Build 5807290117

• 33 of 45 (73.33%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 87.213%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/worker/worker.go	16	28	57.14%
<!--	Total:	33	45	73.33%	-->

Totals
Change from base Build 5795633258:	0.03%
Covered Lines:	6186
Relevant Lines:	7093

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💛 - Coveralls