Make Auto parsing failure print the Label

[wthrowe]

Example output:

In group SpatialDiscretization:
In group DiscontinuousGalerkin:
While parsing option TciOptions:
While creating a TciOptions:
While parsing option MagneticFieldCutoff:
While creating a Auto:
While creating a variant:
At line 67 column 28:
Failed to convert value to type AutoLabel or double: bla

Possible errors:

While creating a variant:
While creating a AutoLabel:
At line 67 column 28:
Failed to parse as Auto label "DoNotCheckMagneticField"

While creating a variant:
At line 67 column 28:
Failed to convert value to type double: bla
############ ERROR ############

This is not quite the issue from #2654, which is about the displayed name rather than the error message.

Proposed changes

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[knelli2]

gcc-10 failure dealt with by #5780 .