Strive for 100 percent (Line) coverage in CI/Tests

[ckormanyos]

[ckormanyos]

A lot of the missing lines in those approximately 3% of missing code coverage are used in I/O streaming, in particular with octal and hexadecimal formats and some less common stream flags.

There also seem to be some missing lines when shif operators get excessive shift amounts.

As usual, we need to handle I/O streaming and certain edge cases better. Use for this the already existing edge-case test file test_uintwide_t_edge_cases.cpp.