feat: add optional async worker backed by PG

[sudo-suhas]

• Bump Go version {1.16 => 1.20} in go.mod and CI.
• Add new command 'compass worker start' to run the async worker as a process.
• Add the pkg/worker pkg for a async worker implementation backed by PostgreSQL. Add sub pkg pgq for enqueueing and processing jobs. Add migrations for tables jobs_queue and dead_jobs.
• Add internal/workermanager pkg for encapsulating Compass service specific enqueue and job functions.
• Introduce async jobs for indexing asset into Elasticsearch and deleting an asset from Elasticsearch. Async jobs are enqueued and processed only if it is enabled in the config. Otherwise, the jobs are executed in-situ.

[coveralls]

Pull Request Test Coverage Report for Build 5640884438

• 518 of 562 (92.17%) changed or added relevant lines in 14 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.4%) to 87.763%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/workermanager/in_situ_worker.go	15	16	93.75%
pkg/worker/backoff_strategy.go	19	20	95.0%
internal/store/postgres/postgres.go	5	8	62.5%
internal/workermanager/discovery_worker.go	57	61	93.44%
pkg/worker/worker.go	109	114	95.61%
internal/workermanager/worker_manager.go	39	47	82.98%
pkg/worker/pgq/pgq_processor.go	58	66	87.88%
pkg/worker/pgq/pgq_utils.go	102	116	87.93%
<!--	Total:	518	562	92.17%	-->

Files with Coverage Reduction	New Missed Lines	%
internal/store/postgres/postgres.go	2	61.64%
<!--	Total:	2		-->

Totals
Change from base Build 5472785716:	0.4%
Covered Lines:	5802
Relevant Lines:	6611

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💛 - Coveralls