feat: enable local proxy configuration in maven plugin configuration

[mischa-n]

Relates to Issue #5040

Description of Change

CICD-SEC-03 recommends:

1. ... packages are pulled through an internal proxy rather than directly from the internet ...
2. ... pull packages from internal repositories ...

We have solved (2), trust our developers, they trust the developers of the third party libraries in use, and those trust the developers of dependent fourth party libraries ...
Nevertheless, we would like to go one step further and completely disable access to the Internet in our CI/CD pipeline.
Therefore, we need to configure a proxy for the dependency-check-maven plugin.

Currently, you can define a proxy to use in the dependency-check-maven plugin via the Maven settings or the system property http.proxyHost.
However, in both cases, the configured proxy is used not only for loading data for analysis, but potentially for dependency resolution as well:

• https://maven.apache.org/guides/mini/guide-proxies.html "... configure a proxy to use for some or all of your HTTP requests with Maven ..."
• https://www.baeldung.com/maven-behind-proxy

With the proposed change, a local proxy can be configured for the dependency-check-maven plugin, which is then used exclusively for loading the analysis data:

<configuration>
	...
	<proxy>
		<host>myproxy</host>
		<port>1234</port>
	</proxy>
	...
</configuration>

Have test cases been added to cover the new functionality?

no

[jeremylong]

Any place we are accepting credentials we should allow this to be retrieved from the settings.xml.

[mischa-n]

@jeremylong : is there anything else I can do here to get the PR accepted?

[jeremylong]

Sorry about the delay - thanks for the PR!