[analyzer] StdLibraryFunctionsChecker: fix bug with arg constraints

[analyzer] StdLibraryFunctionsChecker: fix bug with arg constraints

Summary:
Previously we induced a state split if there were multiple argument
constraints given for a function. This was because we called
`addTransition` inside the for loop.
The fix is to is to store the state and apply the next argument
constraint on that. And once the loop is finished we call `addTransition`.

Reviewers: NoQ, Szelethus, baloghadamsoftware

Subscribers: whisperity, xazax.hun, szepet, rnkovacs, a.sidorin, mikhail.ramalho, donat.nagy, dkrupp, gamesh411, C

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76790