Uniform IPAddress::ToSensitiveString() behavior (debug vs release).

Having a function that changes its behavior based on the build
flavor (debug vs release) is error prone, especially if considered
that the behavior change invalidates the expectation from the function
name itself.

If this feature is required to improve debugging, it should be behind
a macro (for example WEBRTC_LOG_FULL_IP_ADDRESSES) enabled by an
explicit build configuration which is turned OFF by default.

Bug: None
Change-Id: Id7adafc67d1ae674a3dbb382b16ad9faea59eba6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215064
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33800}