preprocessor: improve errors

[BrettMayson]

Show the file stack for redefines when the position is the same for both

Tell the user that __EXEC is not supported

Provide more unique helps for invalid values in configs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.8%. Comparing base (7b8535f) to head (ce308f7).
Report is 2 commits behind head on main.

Additional details and impacted files

Files with missing lines	Coverage Δ
libs/config/src/analyze/lints/c01_invalid_value.rs	75.8% <100.0%> (+0.8%)	⬆️
...s/preprocessor/src/codes/pe10_function_as_value.rs	100.0% <ø> (ø)
...essor/src/codes/pe11_expected_function_or_value.rs	94.5% <ø> (ø)
...s/preprocessor/src/codes/pe12_include_not_found.rs	100.0% <ø> (ø)
...preprocessor/src/codes/pe13_include_not_encased.rs	93.1% <ø> (ø)
...cessor/src/codes/pe14_include_unexpected_suffix.rs	100.0% <ø> (ø)
...preprocessor/src/codes/pe15_if_invalid_operator.rs	84.2% <ø> (ø)
...eprocessor/src/codes/pe16_if_incompatible_types.rs	77.4% <ø> (ø)
libs/preprocessor/src/codes/pe17_double_else.rs	100.0% <ø> (ø)
libs/preprocessor/src/codes/pe18_eoi_ifstate.rs	100.0% <ø> (ø)
... and 22 more

... and 3 files with indirect coverage changes