Improve linefeeds for internal error message

[bradcray]

Getting an internal error today, I was puzzling over the varying line lengths in the message:

         11111111112222222222333333333344444444445555555555666666666677777777778
12345678901234567890123456789012345678901234567890123456789012345678901234567890
--------------------------------------------------------------------------------
Internal errors indicate a bug in the Chapel compiler,
and we're sorry for the hassle.  We would appreciate your reporting this bug --
please see https://chapel-lang.org/bugs.html for instructions.

I think this is an artifact of the rewording in #21676 in which some words were removed and the source code was reformatted to fill 80 columns, but the message itself wasn't. It seems to me as though a better 80-column message would be:

         11111111112222222222333333333344444444445555555555666666666677777777778
12345678901234567890123456789012345678901234567890123456789012345678901234567890
--------------------------------------------------------------------------------
Internal errors indicate a bug in the Chapel compiler, and we're sorry for the
hassle.  We would appreciate your reporting this bug -- please see
https://chapel-lang.org/bugs.html for instructions.

or perhaps:

         11111111112222222222333333333344444444445555555555666666666677777777778
12345678901234567890123456789012345678901234567890123456789012345678901234567890
--------------------------------------------------------------------------------
Internal errors indicate a bug in the Chapel compiler, and we're sorry for the
hassle.  We would appreciate your reporting this bug -- for instructions, please
see: https://chapel-lang.org/bugs.html

I could also imagine removing all linefeeds from the message, but would probably save that until we had a general-purpose "format errors to n columns" capability (because as annoying as it is to get the message, it could be more annoying if it were hard to read).