Support conversion of .boc.txt files (textual BOC) to Fift code

Often, developers copy cell data from TonViewer or similar sources in textual format. In order to work with this data in Fift, additional scripts are required to manually convert the textual BOC into a usable format.

Add native support for converting .boc.txt files (text representation of BOC) into Fift code. This could significantly simplify debugging and manual inspection workflows