Improve exception message for request/response header too large

[cowwoc]

Jetty version(s): 11.0.11

Enhancement Description

When the request or response headers are too large, Jetty throws an exception stating Request header too large or Response header too large.

Is it possible to provide additional information such as: Header size X was greater than HttpClient.requestBufferSize Y.

This helps in two ways:

1. It gives the user a rough idea of how big the buffer needs to be.
2. It gives the user a hint of which HttpClient property needs to be modified.

[cowwoc]

Additionally, it would be useful to view the offending header value. Even seeing a truncated value would help the user establish whether the client or server needs to be modified.

[joakime]

This can be tricky, because on the server side you don't want to reveal any kind of configuration based information in an exception message as those can flow back to the user in various ways.

Traditionally, these are DEBUG logging messages, and improving those is definitely on the table.

[cowwoc]

DEBUG logs are fine with me.

[github-actions]

This issue has been automatically marked as stale because it has been a
full year without activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[sbordet]

This can be solved as part of #5685.