Issues 80: Fix typos in src/exec_state.cpp and src/parquet_impl.cpp

[za-arthur]

• Fix typos in src/exec_state.cpp and src/parquet_impl.cpp mentioned in the issue Statistics not collected on parquet_fdw's foreign table (causing suboptimal planning, leaving a lot of perf on the table) #80
• Fix clang warnings:

warning: moving a temporary object prevents copy elision [-Wpessimizing-move]
...
warning: ‘festate’ may be used uninitialized [-Wmaybe-uninitialized]
...
warning: declaration of ‘path’ shadows a previous local [-Wshadow=compatible-local]