Backport: Improve type-inference in multiplying with TimesOperator

[codecov[bot]]

Codecov Report

Patch coverage: 87.50% and project coverage change: -3.10% :warning:

Comparison is base (51f6c82) 71.29% compared to head (3520f89) 68.19%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## backport_0.8 #588 +/- ## ================================================ - Coverage 71.29% 68.19% -3.10% ================================================ Files 81 81 Lines 8584 8590 +6 ================================================ - Hits 6120 5858 -262 - Misses 2464 2732 +268 ``` | [Files Changed](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/Operators/general/algebra.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9nZW5lcmFsL2FsZ2VicmEuamw=) | `87.91% <85.71%> (-2.22%)` | :arrow_down: | | [src/Operators/banded/Multiplication.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/588?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9iYW5kZWQvTXVsdGlwbGljYXRpb24uamw=) | `76.54% <88.88%> (-0.38%)` | :arrow_down: | ... and [33 files with indirect coverage changes](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/588/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation)

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