Store domainspace in TimesOperator

[jishnub]

This makes the domainspace of a TimesOperator type-inferred

julia> @inferred domainspace(Derivative() * Multiplication(Fun(), Chebyshev()))
Chebyshev()

[codecov]

Codecov Report

Patch coverage: 87.50% and project coverage change: -47.47% ⚠️

Comparison is base (28eb4ea) 75.24% compared to head (d1fcd94) 27.77%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #440       +/-   ##
===========================================
- Coverage   75.24%   27.77%   -47.47%     
===========================================
  Files          80       80               
  Lines        8421     8406       -15     
===========================================
- Hits         6336     2335     -4001     
- Misses       2085     6071     +3986     

Files Changed	Coverage Δ
src/Spaces/ConstantSpace.jl	14.87% <77.77%> (-42.39%)	⬇️
src/Operators/general/algebra.jl	66.84% <100.00%> (-25.80%)	⬇️
src/show.jl	62.96% <100.00%> (-34.26%)	⬇️

... and 68 files with indirect coverage changes

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