chore: use namespace concrete for the py package

Compiler tools such as CompilerEngine would now be imported from
concrete.compiler
Dialects would now be imported from concrete.lang.dialects
And anything related to concretelang can be imported directly from
concrete.lang

compiler/tests/python/test_compiler_engine.py

@@ -3,7 +3,7 @@ import tempfile
 
 import pytest
 import numpy as np
-from concretelang import CompilerEngine, library
+from concrete.compiler import CompilerEngine, library
 
 KEY_SET_CACHE_PATH =  os.path.join(tempfile.gettempdir(), 'KeySetCache')
 

compiler/tests/python/test_hlfhe_dialect.py

@@ -1,7 +1,7 @@
 import pytest
 from mlir.ir import Context, RankedTensorType, Location
-from concretelang import register_dialects
-from concretelang.dialects import hlfhe
+from concrete.lang import register_dialects
+from concrete.lang.dialects import hlfhe
 
 
 @pytest.mark.parametrize("width", list(range(1, 8)))

compiler/tests/python/test_round_trip.py

@@ -1,5 +1,5 @@
 import pytest
-from concretelang import compiler
+from concrete import compiler
 
 
 VALID_INPUTS = [