Fix complex log1p accuracy with large abs values. (#88364)

This ports openxla/xla#10503 by @pearu. In addition to the filecheck
test here, the accuracy was tested with XLA's complex_unary_op_test and
its MLIR emitters.

This is a fixed version of
https://github.com/llvm/llvm-project/pull/88260. The previous version
relied on implementation-specific behavior in the order of evaluation of
maxAbsOfRealPlusOneAndImagMinusOne's operands.