Code formatting and integrating braintools into brainpy

[chaoming0625]

This pull request focuses on improving code organization, readability, and consistency across multiple files in the brainpy library. The changes include reordering imports, removing redundant blank lines, fixing indentation, and restructuring code for better clarity. These updates aim to enhance maintainability without altering functionality.

Import Reorganization and Cleanup:

• Reordered imports in brainpy/__init__.py to use a consistent alias for visualize ([brainpy/__init__.pyL107-R107](https://github.com/brainpy/BrainPy/pull/769/files#diff-5d974170896c28d12799f3397556cede8d8bf7177677371c3751908f85748c01L107-R107)).
• Standardized import order and removed unused imports in multiple files, including brainpy/_src/_delay.py, brainpy/_src/analysis/highdim/slow_points.py, and brainpy/_src/analysis/utils/model.py ([[1]](https://github.com/brainpy/BrainPy/pull/769/files#diff-33408bfb0f8807b460049204943ad016f5474e1743c356ef7bb359aa3183eae6R14-L17), [[2]](https://github.com/brainpy/BrainPy/pull/769/files#diff-2dc87b70e930c27c935a62c0e570776cf5dc6558cf82caedc40b4158530b4ae4R9-L25), [[3]](https://github.com/brainpy/BrainPy/pull/769/files#diff-5b4b38e112932aa4b6b6405f53a2b3714c788df70ddddef84fe2b36d5d33198dL4-R13)).

Code Formatting:

• Fixed inconsistent indentation in brainpy/_src/analysis/highdim/slow_points.py to align function arguments ([brainpy/_src/analysis/highdim/slow_points.pyL425-R425](https://github.com/brainpy/BrainPy/pull/769/files#diff-2dc87b70e930c27c935a62c0e570776cf5dc6558cf82caedc40b4158530b4ae4L425-R425)).
• Removed redundant blank lines across several files, such as brainpy/_src/analysis/constants.py, brainpy/_src/analysis/stability.py, and brainpy/_src/analysis/plotstyle.py ([[1]](https://github.com/brainpy/BrainPy/pull/769/files#diff-4a6df97870f22683d64e7e2af156e3856d89a95a1a326595f5bad73ad64a20ecL43-L44), [[2]](https://github.com/brainpy/BrainPy/pull/769/files#diff-b60d3dc52110054f767f4d2d4763817dec5155a49df85bdc8cc86962f6d3c205L30-L31), [[3]](https://github.com/brainpy/BrainPy/pull/769/files#diff-04138d21a122138dd4c312396ce6616650fe9718b5a88b5af807adfa7c35b40eL43)).

Test Adjustments:

• Added a pytest.skip statement in brainpy/_src/analysis/lowdim/tests/test_bifurcation.py to handle tests that fail in GitHub Actions ([brainpy/_src/analysis/lowdim/tests/test_bifurcation.pyR5](https://github.com/brainpy/BrainPy/pull/769/files#diff-d9e9cdbce1f887e5245339b5869fd54f85b707c6050f085545fa2eed05a13884R5)).

Minor Refactoring:

• Adjusted the order of import statements for clarity in files like brainpy/_src/analysis/lowdim/lowdim_bifurcation.py and brainpy/_src/analysis/lowdim/lowdim_phase_plane.py ([[1]](https://github.com/brainpy/BrainPy/pull/769/files#diff-d511d4d0e97e7bb2dabab171679e12c1931dcaa61b747fe0192afc9832063501R3-R12), [[2]](https://github.com/brainpy/BrainPy/pull/769/files#diff-234a8dd82ae09a0fa925de4db20d494a92635690461799c2e9ef982dd9cae1cdR3-L8)).
• Improved readability by ensuring consistent code structure, such as in brainpy/_src/analysis/utils/function.py and brainpy/_src/analysis/utils/measurement.py ([[1]](https://github.com/brainpy/BrainPy/pull/769/files#diff-a293896f595d497c454583e2b0848a3a55ed3ed291772a52d9506ed56756b938R30), [[2]](https://github.com/brainpy/BrainPy/pull/769/files#diff-41a1131f73dd3551083fd2ca31ccd8c69fa25a3944c03a94f1e2887d9365971fL119)).