Move more code out of src/Hecke*.jl

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0.59880% with 166 lines in your changes missing coverage. Please review.

Project coverage is 85.98%. Comparing base (f44f726) to head (7854de1).

Files	Patch %	Lines
src/antic/nf_elem.jl	0.00%	53 Missing :warning:
src/flint/fmpz_mat.jl	0.00%	43 Missing :warning:
src/flint/gfp_elem.jl	0.00%	15 Missing :warning:
src/julia/Integer.jl	0.00%	12 Missing :warning:
src/flint/fmpz_mod.jl	0.00%	9 Missing :warning:
src/flint/nmod.jl	0.00%	9 Missing :warning:
src/flint/fmpz.jl	0.00%	7 Missing :warning:
src/flint/gfp_fmpz_elem.jl	0.00%	5 Missing :warning:
src/flint/fmpq.jl	0.00%	3 Missing :warning:
src/flint/fmpq_mpoly.jl	0.00%	3 Missing :warning:
... and 4 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1804 +/- ## ========================================== + Coverage 85.94% 85.98% +0.03% ========================================== Files 95 98 +3 Lines 36387 36380 -7 ========================================== + Hits 31272 31280 +8 + Misses 5115 5100 -15 ```

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[fingolfin]

Rebased