chore(nodebuilder/das | pruner): Privatise `samplingWindow` in DAS params, add Duration method to `AvailabilityWindow` #7528

Job	Run time
setup	1s
yamllint	12s
Markdown Lint	11s
hadolint / hadolint	6s
go-ci / Setup	1s
go-ci / Lint	1m 53s
go-ci / Go Mod Tidy Check	13s
go-ci / Unit Tests Coverage (ubuntu-latest)	3m 33s
go-ci / Unit Tests Coverage (macos-14)	2m 29s
go-ci / Integration Tests / Da Tests Sync	2m 5s
go-ci / Integration Tests / Integration Tests API	2m 17s
go-ci / Integration Tests / Integration Tests Blob	2m 14s
go-ci / Integration Tests / Integration Tests Fraud	2m 42s
go-ci / Integration Tests / Integration Tests ND	2m 13s
go-ci / Integration Tests / Integration Tests p2p	2m 6s
go-ci / Integration Tests / Integration Tests Reconstruction	2m 3s
go-ci / Integration Tests / Integration Tests Sync	2m 38s
version_bump	3s
goreleaser	0s
	27m 0s

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