Adding BaseUnits for Angstrom results in test failures due to UnitSystem logic

[tmilnthorp]

Describe the bug
Adding BaseUnits for Angstrom results in test failures due to UnitSystem logic. The BaseUnits for Armstrongs are coming as the first QuantityInfo in the UnitSystem constructor since A happens to be first in the alphabetic list.

To Reproduce
Steps to reproduce the behavior (just an example):

• Make sure Armstrongs are in the code (see Add Angstrom unit #1042)
• Add BaseUnits of Meter

Expected behavior
Meters is still the expected LengthUnit for SI.

Screenshots

[lipchev]

@angularsen I've just added the Angstrom in 2d5ead8 and nothing broke (we're correctly getting Meters from the constructor).
CC @tmilnthorp

[angularsen]

Very nice 👏

[lipchev]

One way or another, I think this can be considered as resolved by #1473