[TM-372] `failCustom_` is inefficient

Description

It seems like that failCustom_ function produced the following stack of instructionsunit; push _; pair, but it can do only one push with pair argument, so this MR refactors failCustom_ so it uses just two instructions: PUSH and FAILWITH.

Related issue(s)

https://issues.serokell.io/issue/TM-372

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