Duplicate exp functions

[gztensor]

We have duplicate exponentiation functions in the math.rs file:

1. subtensor/pallets/subtensor/src/epoch/math.rs

   Line 172 in ae2b373

   pub fn exp_safe(input: I32F32) -> I32F32 {

2. subtensor/pallets/subtensor/src/epoch/math.rs

   Line 1597 in ae2b373

   pub fn safe_exp(value: I32F32) -> I32F32 {

Review if they are equivalent and refactor/fix as needed.

[MkDev11]

The functions are NOT equivalent, but they are confusingly named and serve similar purposes:

exp_safe is more robust—it pre-clamps input to prevent overflow and has smarter error handling (returns max_value for large positive inputs that overflow)
safe_exp is a simple wrapper that just returns 0 on any error