Add COPT support for PuLP

[wujianjack]

This PR adds COPT support for PuLP, including COPT_CMD(), COPT_DLL() and COPT() solvers.

The COPT_CMD() and COPT_DLL() solvers depend on copt_cmd and COPT shared library respectively, so a full installation of COPT package is required. You can obtain the latest packages from https://github.com/COPT-Public/COPT-Release.

The COPT() solver depends on coptpy, you can install with pip install coptpy.

For larger instances, a valid COPT license is required, you can apply one from https://www.shanshu.ai/copt.

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[pchtsp]

this is great! It would be great to add these solvers to the tests, like here:

pulp/pulp/tests/test_pulp.py

Lines 1479 to 1481 in a7684ac

	class HiGHS_CMDTest(BaseSolverTest.PuLPTest):
	solveInst = HiGHS_CMD

And also it would be even greater to add the installation of the python package in the integrated tests:

pulp/.github/workflows/pythonpackage.yml

Lines 29 to 32 in a7684ac

	- name: Install highspy
	if: matrix.os == 'ubuntu-latest' || matrix.os == 'macOS-latest'
	run: |
	pip install highspy

by adding another step with the installation of the package.

[wujianjack]

this is great! It would be great to add these solvers to the tests, like here:

pulp/pulp/tests/test_pulp.py

Lines 1479 to 1481 in a7684ac

	class HiGHS_CMDTest(BaseSolverTest.PuLPTest):
	solveInst = HiGHS_CMD

And also it would be even greater to add the installation of the python package in the integrated tests:

pulp/.github/workflows/pythonpackage.yml

Lines 29 to 32 in a7684ac

	- name: Install highspy
	if: matrix.os == 'ubuntu-latest' || matrix.os == 'macOS-latest'
	run: |
	pip install highspy

by adding another step with the installation of the package.

@pchtsp Thanks! Please check the updates.

[pchtsp]

hello! it seems that the tests are falling. Could you take a look? Are you sure the COPT_HOME env variable is set?

[wujianjack]

hello! it seems that the tests are falling. Could you take a look? Are you sure the COPT_HOME env variable is set?

Ah, the COPT_DLL requires the libcopt.so and COPT_HOME which requires some setup steps, can we just run the tests with COPT so that pip install coptpy is enough.

It would be nice to test with COPT_CMD and COPT_DLL also, but I don't know how to setup correctly in CI.