simplify the imports in test

Author: ytdHuang

test/core-test/generalized_master_equation.jl

@@ -1,7 +1,7 @@
 @testitem "Generalized Master Equation" default_imports=false begin
     using Test
     using QuantumToolbox
-    import LinearAlgebra: triu
+    using LinearAlgebra
 
     N_c = 30
     N_trunc = 10

test/core-test/low_rank_dynamics.jl

@@ -1,7 +1,7 @@
 @testitem "Low Rank Dynamics" default_imports=false begin
     using Test
     using QuantumToolbox
-    import LinearAlgebra: Diagonal, mul!
+    using LinearAlgebra
 
     # Define lattice
     Nx, Ny = 2, 3

test/core-test/quantum_objects.jl

@@ -1,11 +1,9 @@
 @testitem "Quantum Objects" default_imports=false begin
     using Test
     using QuantumToolbox
-
-    # Importing only the necessary functions to keep track the re-export of the functions
-    import LinearAlgebra: I, triu, tril, triu!, tril!
-    import SparseArrays: sparse, sprand, spzeros, nnz, SparseVector, SparseMatrixCSC
-    import StaticArraysCore: SVector
+    using LinearAlgebra
+    using SparseArrays
+    using StaticArraysCore
 
     # ArgumentError: type is incompatible with vector or matrix
     @testset "ArgumentError" begin

test/core-test/quantum_objects_evo.jl

@@ -1,12 +1,10 @@
 @testitem "Quantum Objects Evolution" default_imports=false begin
     using Test
     using QuantumToolbox
-
-    # Importing only the necessary functions to keep track the re-export of the functions
-    import LinearAlgebra: I
-    import SparseArrays: sprand
-    import StaticArraysCore: SVector
-    import SciMLOperators: MatrixOperator, NullOperator, IdentityOperator
+    using LinearAlgebra
+    using SparseArrays
+    using StaticArraysCore
+    using SciMLOperators
 
     # DomainError: incompatible between size of array and type
     @testset "Thrown Errors" begin

test/core-test/states_and_operators.jl

@@ -2,10 +2,8 @@
     using Test
     using QuantumToolbox
     import QuantumToolbox: position, momentum
-
-    # Importing only the necessary functions to keep track the re-export of the functions
-    import LinearAlgebra: I
-    import SparseArrays: sparse, spzeros, spdiagm, SparseMatrixCSC, AbstractSparseMatrix
+    using LinearAlgebra
+    using SparseArrays
 
     @testset "zero state" begin
         v1 = zero_ket(4)

test/core-test/time_evolution.jl

@@ -1,8 +1,8 @@
 @testitem "Time Evolution and Partial Trace" default_imports=false begin
     using Test
     using QuantumToolbox
-    import Random: MersenneTwister
-    import SciMLOperators: MatrixOperator
+    using Random
+    using SciMLOperators
 
     # Global definition of the system
     N = 10