Significantly rework `ConfigurationPropertyName` in an attempt to reduce
the amount of memory and garbage produced. The name elements are now
stored as CharSequences and whenever possible subsequences are used.

This helps to reduce the memory footprint since the underlying char
array can be shared between the source string, and the individual
elements.

For example: `ConfigurationProperty.of("foo.bar.baz")` will return
a name that provides access to the elements `foo`, `bar` and `baz`.
However, these three names all share the same char[], just using
different offsets and lengths.

See gh-9000