[HttpClientFactory] Don't log header values by default

[CarnaViire]

Only affects the default case; if the sensitive headers were ever specified by RedactLoggedHeaders, the behavior is unchanged.

[rokonec]

LGTM. Only concern is about performance, but I suppose in default we do not log header values so by default perf is not affected by redacting.

[MihaZupan]

Are we treating this as a breaking change?

[CarnaViire]

Only concern is about performance, but I suppose in default we do not log header values so by default perf is not affected by redacting.

@rokonec yeah, these are Trace level logs. And it doesn't matter much from perf perspective whether the value is redacted or not because nothing need to be parsed; FWIW it will be only faster with the redaction on, see HttpHeadersLogValue.ToString() 😄

Are we treating this as a breaking change?

@MihaZupan Yes, we should; there is some tag I need to apply here then, right?

[dotnet-policy-service]

Added needs-breaking-change-doc-created label because this PR has the breaking-change label.

When you commit this breaking change:

1. Create and link to this PR and the issue a matching issue in the dotnet/docs repo using the breaking change documentation template, then remove this needs-breaking-change-doc-created label.
2. Ask a committer to mail the .NET Breaking Change Notification DL.

Tagging @dotnet/compat for awareness of the breaking change.

[CarnaViire]

/ba-g DeadLetter Helix crash on an unrelated test run (System.Runtime.Tests on ios-arm64)