Consider getting rid of string index data file

[michaelwoerister]

The new file encoding for the string table introduced in #90 still has some unused bit-prefixes in its grammar that would allow it to efficiently (i.e. without additional space overhead) encode the string index data table as part of the regular string table data. The index entries would just be interspersed with the string components and the grammar would make sure that we can parse them out properly again.

The only reason I'm a bit hesitant to implement this is that it would require tools to always parse the entire string table once on startup in order to find all the index entries. It's just a single pass and the parsing is not more complicated than parsing a huge UTF-8 string, but it would add a bit of overhead to every tool invocation.

On the positive side it would allow us to get rid of one of the three files we generate when recording a profile.

[Mark-Simulacrum]

I am in favor of reducing the number of files. I suspect the cost of parsing the huge UTF-8 string is pretty low? IIRC, UTF-8 decoding is on-par with disk read speed (or faster) these days.

[michaelwoerister]

I suspect that the slowdown wouldn't be noticeable but I we don't have benchmarks for the tools, I think.