allow for absolute paths in diagnostic reporting

[gadfort]

Is your feature request related to the C++ slang project or the pyslang Python bindings?
C++ slang, but also relates to pyslang

Is your feature request related to a problem? Please describe.
When reporting paths, slang is currently responding with relative paths
../../../../../gcd.v:188:28: warning:
which makes finding the path to the file somewhat difficult.

Describe the solution you'd like
Provide an option to report the paths in absolute/canonical paths:
like
/data/verilog/examples/gcd/gcd.v:188:28: warning:
Either by a flag in the SourceManager or TextDiagnosticClient or where it make most sense to control it (and it should have a binding in pyslang too)

Describe alternatives you've considered
N/A

Additional context
N/A