Allow URI Filenames for SQLite Input and Output

[cwarden]

When a file: or :memory: filename is used for a sqlite input or output
directive, pass directly to sqlite3_open() as-is rather than prepending
the fact directory to the filename.

[codecov]

Codecov Report

Merging #2177 (d11266f) into master (5bef4c1) will increase coverage by 0.20%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master    #2177      +/-   ##
==========================================
+ Coverage   75.34%   75.54%   +0.20%     
==========================================
  Files         450      452       +2     
  Lines       27283    27253      -30     
==========================================
+ Hits        20556    20589      +33     
+ Misses       6727     6664      -63     

Impacted Files	Coverage Δ
src/include/souffle/io/ReadStreamSQLite.h	76.08% <50.00%> (-0.58%)	⬇️
src/include/souffle/io/WriteStreamSQLite.h	69.54% <100.00%> (+0.35%)	⬆️
src/ast/transform/SemanticChecker.cpp	96.71% <0.00%> (ø)
src/ast/transform/SubsumptionQualifier.h	50.00% <0.00%> (ø)
src/ast/transform/SubsumptionQualifier.cpp	100.00% <0.00%> (ø)
src/interpreter/Engine.cpp	89.97% <0.00%> (+0.02%)	⬆️
src/main.cpp	68.07% <0.00%> (+0.09%)	⬆️
...ouffle/datastructure/ConcurrentInsertOnlyHashMap.h	90.90% <0.00%> (+1.81%)	⬆️
src/parser/ParserUtils.cpp	77.50% <0.00%> (+2.50%)	⬆️
src/ast/utility/Utils.cpp	91.47% <0.00%> (+3.41%)	⬆️
... and 2 more

[b-scholz]

Thanks for the contribution!