Add netty request decoder customizer

[ssko1]

When making the jump from Tomcat to Netty, I noticed that my -Dserver.max-http-header-size configuration was not being honored. This PR allows users to configure the netty HttpRequestDecoderSpec using ServerProperties.

Notes on implementation

• (serverProperties max-http-header-size of <= 0 will defer to serverProperties.netty maxHeaderSize)

[snicoll]

@CinnamonBagels thanks a lot for the PR but we already have an issue for this (#13831) and a PR (#14234). We'd rather fix the server.max-http-header-size situation first.

The other part of this PR look unrelated to the task at hand. We usually expose first class properties based on a concrete scenario. Can you please share why you believe those properties would be useful vs. a programmatic customizer?

[ssko1]

I added all of the configuration options that HttpRequestDecoderSpec allowed on a nice-to-have basis. Now I understand the reasons why properties are exposed, so my changes don't make sense yet. Thanks for pointing me to the issue and PR and giving feedback.

[snicoll]

Alright, thanks for the PR anyway.