[flang] Revert 3 commits pushed by mistake along b7c07ce1

Revert "[flang][NFC] Add debug dump method to evaluate::Expr and semantics::Symbol"
This reverts commit b0e35fde.

Revert "[flang] Add a wrapper for Fortran main program"
This reverts commit 2c1ce075.

Revert "[flang][NFC] Fix header comments in some runtime headers"
This reverts commit a63f5767.