Z3encoding: Add bad tests related to dates [skip ci]

tests/test_proof/bad/dates_simple-empty.catala_en

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+## Test
+
+```catala
+declaration scope A:
+  context x content date
+  context y content boolean
+
+scope A:
+  definition x equals |2022-01-16|
+  definition y under condition x >=@ |2010-01-01| and x <@ |2015-01-01| consequence equals false
+  definition y under condition x >=@ |2015-01-01| and x <@ |2020-01-01| consequence equals true
+  definition y under condition x >=@ |2020-01-01| consequence equals false
+```

tests/test_proof/bad/dates_simple-overlap.catala_en

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+## Test
+
+```catala
+declaration scope A:
+  context x content date
+  context y content boolean
+
+scope A:
+  definition x equals |2022-01-16|
+  definition y under condition x <=@ |2010-01-01| consequence equals true
+  definition y under condition x >=@ |2010-01-01| and x <@ |2015-01-01| consequence equals false
+  definition y under condition x >=@ |2015-01-01| and x <@ |2020-01-01| consequence equals true
+  definition y under condition x >=@ |2020-01-01| consequence equals false
+```

tests/test_proof/bad/output/dates_simple-empty.catala_en.Proof

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+[ERROR] The translation to Z3 failed:
+TODO
+[ERROR] The translation to Z3 failed:
+TODO
+[RESULT] [A.x] This variable never returns an empty error
+[RESULT] [A.x] No two exceptions to ever overlap for this variable

tests/test_proof/bad/output/dates_simple-overlap.catala_en.Proof

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+[ERROR] The translation to Z3 failed:
+TODO
+[ERROR] The translation to Z3 failed:
+TODO
+[RESULT] [A.x] This variable never returns an empty error
+[RESULT] [A.x] No two exceptions to ever overlap for this variable