Improvement: Fix `DeepFilterNetCommandBuilder::setInputFile()` limitation

[omeryusufyagci]

Due to a limitation of the underlying model, we cannot pass an input file flag (for OS calling).
This causes an issue where the user has to know when to call the setInputFile() method first, which diverges from the builder pattern, and is just not nice.

We need a solution for this without sacrificing the const-correctness and diverging from the pattern.

More details in the DeepFilterCommandBuilder.h file.

[nikhiljangra264]

I saw this when making test cases.
Is it solved?
@omeryusufyagci

One way is to store all the arguments first and calling addArgument or addFlag in required sequence in build function.

or adding another function which adds the flag in front of the command instead of pushing back. can be useful in many cases like command name.