Rollup merge of #55919 - Turbo87:num-tests, r=dtolnay
Rollup merge of #55919 - Turbo87:num-tests, r=dtolnay

core/tests/num: Simplify `test_int_from_str_overflow()` test code

This commit changes the test code to compare against easier-to-read, static values instead of relying on the result of `wrapping_add()` which may or may not result in the value that we expect.

aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust