[flang][driver] Modify the existing test cases that use -Mstandard in f18, to use -pedantic and %flang_fc1 to share with the new driver
One of the test cases (flang/test/Semantics/dosemantics03.f90) fails currently when tested against the new driver as -Werror is used in addition to -pedantic in that test. When -Werror lands (https://reviews.llvm.org/D98657) for the new driver, this error will go away.