kmir execution should be enabled for any functions

[yanliu18]

mir-semantics/kmir/k-src/mir.md

Line 37 in e0d53af

rule <k> #initialized() => #executeFunctionLike(Fn(String2IdentifierToken("main"):: .FunctionPath), .ArgumentList) ... </k>

The above implementation ensures a MIR file always starts with the main function, which is consistent with the rust code execution rules.

However, we should allow MIR file to analyse any functions, for example, kmir should be able to execute the add function.

In this way, we treat functions as the main unit for analysis rather than the rust code file, enabling more flexibility.