Introducing models of ducted fan propulsion

[ngomezve]

This PR introduces a new propulsion architecture to TASOPT: ducted fans. These fans are assumed to be powered by a system that can provide mechanical power (e.g., an electric motor). Models for motors and cables are currently in development by @askprash, but have not been pulled in yet.

The ducted fan models are based on the existing turbofan models, but the core has been removed. Two functions are introduced: ductedfansize!() sizes the ducted fan for a desired mission point and ductedfanoper!() calculates the off-design performance for specified power or thrust.

The function ductedfanoper!() solves a small non-linear problem by using the NLsolve.jl suite. This is not as efficient as the direct Jacobian computation in tfoper!() but is easier to modify.

[codecov]

Codecov Report

Attention: Patch coverage is 61.88605% with 194 lines in your changes missing coverage. Please review.

Project coverage is 72.57%. Comparing base (430cfd8) to head (feb81f4).
Report is 46 commits behind head on main.

Files with missing lines	Patch %	Lines
src/engine/ducted_fan/ductedfancalc.jl	0.00%	141 Missing ⚠️
src/engine/ducted_fan/ductedfanweight.jl	0.00%	28 Missing ⚠️
src/engine/ducted_fan/ductedfansize.jl	85.84%	15 Missing ⚠️
src/engine/ducted_fan/ductedfanoper.jl	95.72%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #104      +/-   ##
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- Coverage   73.41%   72.57%   -0.84%     
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  Files          77       84       +7     
  Lines       13908    13997      +89     
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- Hits        10211    10159      -52     
- Misses       3697     3838     +141     

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