reorganise files in estimation folder #3068

Job	Run time
Tests vs fixest (ubuntu-latest, 3.9, --workers 4 --tests-per-worker 1)	23m 47s
Build Docs	12m 0s
Tests Core (ubuntu-latest, 3.9, --workers 4 --tests-per-worker 1)	19m 18s
Tests vs fixest (ubuntu-latest, 3.14, --workers 4 --tests-per-worker 1)	22m 43s
Tests Core (ubuntu-latest, 3.14, --workers 4 --tests-per-worker 1)	19m 48s
Publish Docs	0s
Merge Coverage	0s
	1h 37m 36s

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