Previously, HttpMessageConvertersAutoConfiguration registered
ServerProperties. When this happened in a parent context, any child
contexts would skip registering ServerProperties due to its presence
in the parent context. This prevents the child contexts from
configuring their own server properties.

This commit updates HttpMessageConvertersAutoConfiguration to
bind server.servlet.encoding directly instead of enabling
ServerProperties. With ServerProperties no longer enabled in a parent
context, child contexts are now able to configure their own server
properties.

Fixes gh-21789