Add survey design support to StaggeredTripleDifference #699

Job	Run time
Pure Python Fallback	59m 38s
Rust Unit Tests (ubuntu-24.04-arm)	1m 19s
Rust Unit Tests (macos-latest)	1m 19s
Python Tests (windows-latest, py3.13)	38m 13s
Rust Unit Tests (ubuntu-latest)	1m 19s
Python Tests (ubuntu-latest, py3.13)	37m 24s
Python Tests (windows-latest, py3.11)	37m 52s
Python Tests (macos-latest, py3.11)	18m 22s
Rust Unit Tests (windows-latest)	2m 55s
Python Tests (ubuntu-24.04-arm, py3.11)	18m 28s
Python Tests (ubuntu-24.04-arm, py3.13)	18m 44s
Python Tests (ubuntu-latest, py3.11)	39m 55s
Python Tests (macos-latest, py3.13)	17m 55s
	4h 53m 23s

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