RFR: 8278353: Provide Duke as default favicon in Simple Web Server

[Christian Stein]

Please pre-review this draft pull request adding a default for response for the `/favicon.ico` path to the Simple Web Server introduced by [JEP 408](https://openjdk.org/jeps/408). The image in this PR is a copy of https://inside.java/images/favicon.ico

Before this change, an initial request from a browser yields the following output on the server console:

Binding to loopback by default. For all interfaces use "-b 0.0.0.0" or "-b ::".
Serving PATH and subdirectories on 127.0.0.1 port 8000
URL http://127.0.0.1:8000/
127.0.0.1 - - [30/Apr/2024:13:11:39 +0200] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [30/Apr/2024:13:11:40 +0200] "GET /favicon.ico HTTP/1.1" 404 -


After applying this change set, the two last line read:

127.0.0.1 - - [30/Apr/2024:13:12:08 +0200] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [30/Apr/2024:13:12:08 +0200] "GET /favicon.ico HTTP/1.1" 200 -

-------------

Commit messages:
 - Extract constants for default `favicon.ico`
 - 8278353: Provide Duke as default favicon in Simple Web Server

Changes: https://git.openjdk.org/jdk/pull/19020/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19020&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8278353
  Stats: 104 lines in 4 files changed: 100 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/19020.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19020/head:pull/19020

PR: https://git.openjdk.org/jdk/pull/19020