Add some mpoly context util functions #982

Job	Run time
Test coverage setuptools build	4m 56s
Test docs (build and doctest)	4m 41s
Build wheels for ubuntu-20.04	14m 10s
Build sdist	2m 59s
Build wheels for windows-2019	28m 16s
Test flint main	4m 43s
Build wheels for macos-13	15m 28s
Build wheels for macos-14	8m 20s
Test flint v3.0.0	4m 58s
Free-threaded 3.13-dev on ubuntu-24.04	5m 10s
Test old Cython/meson-python	2m 0s
Test flint v3.0.1	5m 6s
Build on ubuntu-24.04	1m 58s
Test flint v3.1.0	4m 43s
Test SymPy 1.13.1	18m 15s
Test flint v3.1.1	4m 41s
Test flint v3.1.2	4m 44s
Test 3.10 wheel on ubuntu-20.04	6s
Publish to PyPI	0s
Test 3.11 wheel on ubuntu-20.04	5s
Test 3.12 wheel on ubuntu-20.04	7s
Test 3.13-dev wheel on ubuntu-20.04	15s
Test pypy3.10 wheel on ubuntu-20.04	20s
Test 3.10 wheel on windows-2019	17s
Test 3.11 wheel on windows-2019	17s
Test 3.12 wheel on windows-2019	15s
Test 3.13-dev wheel on windows-2019	1m 25s
Test pypy3.10 wheel on windows-2019	31s
Test 3.10 wheel on macos-13	10s
Test 3.11 wheel on macos-13	10s
Test 3.12 wheel on macos-13	13s
Test 3.13-dev wheel on macos-13	44s
Test pypy3.10 wheel on macos-13	12s
Test 3.10 wheel on macos-14	8s
Test 3.11 wheel on macos-14	9s
Test 3.12 wheel on macos-14	9s
Test 3.13-dev wheel on macos-14	26s
Test pypy3.10 wheel on macos-14	21s
Publish GitHub release	0s
	2h 21m 28s

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