[DOP-30631] Add support for Iceberg REST Catalog + S3 delegated access

[dolfinus]

Change Summary

Now Iceberg connection has 2 connection_data schemas - one with S3 URL and params (direct S3 access), another with no S3 params at all (access is delegated to REST Catalog). This makes schema a bit complex for UI to implement, but allows to avoid copy-pasting the entire Iceberg connection logic into new connection class.

Based on MobileTeleSystems/onetl#413.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
syncmaster/dto
connections.py	178	5	97%	146, 153–155, 161
transfers.py	112	1	99%	93
syncmaster/schemas/v1/connections
iceberg.py	46	1	97%	82
syncmaster/worker
controller.py	93	1	98%	257
spark.py	79	2	97%	132–133
syncmaster/worker/handlers/db
iceberg.py	54	4	92%	59, 99, 119, 135
TOTAL	5092	296	94%