AD: adding linearization tests for aerodyn continuous-states model

[ebranlard]

This pull request ready to be merged

Feature or improvement description
Adds two simple test cases for the continuous-states aerodynamic models DBEMT=3, UAMod=4 and UAMod=6. The test also look at the UserProp linearization. These tests are introduced because these aerodyn linearization features were not previously tested. (Time domain tests are present in the aerodyn_driver).

The tests are introduced in preparation for a couple of AeroDyn updates to UA, DBEMT, and the AeroCompMaps in AeroDyn.

See readmes:

• https://github.com/OpenFAST/r-test/tree/f/adlin-tests/glue-codes/openfast/Fake5MW_AeroLin_B1_UA4_DBEMT3
• https://github.com/OpenFAST/r-test/tree/f/adlin-tests/glue-codes/openfast/Fake5MW_AeroLin_B3_UA6

Impacted areas of the software
r-test only, but this is intended towards AeroDyn linearization testing.

Test results, if applicable

The tests are labeled Fake5MW as they only use 4 blade stations, 2 polars, and the last polar is subplemented with an extra table to test the UserProp interpolation. It was verified that the UA and DBEMT models have a decent impact (see figure below for different UA and DBEMT) on the axial induction, and lift, compared to simulations with steady parameters (UA0 DBEMT0). The Jacobian with respect to UserProp are none zero for the 3 sections that use the polar.

Checklist

• Merge r-test branch f/adlin-tests into rtest rc-3.5.1
• Merge r-test: update of lin file comparison #1694