sagemath: update deps (on top of #58320)

[tornaria]

• python3-Cython: patch for sage
• sagemath: update to 10.8.
• python3-cysignals: update to 1.12.6.
• python3-cypari2: update to 2.2.4.
• python3-gmpy2: update to 2.2.2.
• python3-memory_allocator: update to 0.2.0.
• m4ri: update to 20251207.
• m4rie: better changelog
• m4ri: update to 20260122.
• m4rie: rebuild for m4ri-20260122.
• brial: update to 1.2.15.
• ntl: update to 11.6.0.
• ntl: cross build.
• flintlib: update to 3.4.0.
• gap: update to 4.15.1.
• eclib: rebuild for ntl and flintlib
• singular: rebuild for ntl and flintlib
• sagemath: fix some tests
• sagemath: change sphinx

Testing the changes

• I tested the changes in this PR: briefly

This is based on #58320, updating dependencies that would need rebuilding sagemath.

I'm in the process of testing.

Missing / TODO:

• update maxima (see Update to maxima 5.49 sagemath/sage#40679)
• update ipykernel

[tornaria]

@dkwo you may want to try this.

In particular, I made ntl cross, could you make sure that cross built ntl works ok? We also need to adjust flintlib and singular templates so they are built with ntl on cross.