[BOLT] Fixing relative ordering of cold sections under multi-way function splitting

Order code sections with names in the form of ".text.cold.i" based on the value of i

[Context] SplitFunctions.cpp implements splitting strategies that can potentially split each function into maximum N>2 fragments.
When such N-way splitting happens, new code sections with names ".text.cold.1", ..., ".text.cold.i", ... "text.cold.N-2" will be created
A section with name ".text.cold.i" contains the the (i+2)th fragment of each function.
As an example, if each function is splitted into N=3 fragments: hot, warm, cold, then code sections will now include
- a section with name ".text" containing hot fragments
- a section with name ".text.cold" containing warm fragments
- a section with name ".text.cold.1" containing cold fragments

The order of these new sections in the output binary currently depends on the order in which they are encountered by the emitter.
For example, under N=3-way splitting, if the first function is 2-way ...