Move generated live_reload patterns to runtime config

[jechol]

phx.new currently generates live_reload patterns in config/dev.exs.

Those patterns are runtime-only endpoint configuration, read by Phoenix.LiveReloader from the endpoint config when the live reload socket joins. They do not need to be part of compile-time configuration.

Keeping them in compile config can lead to unnecessary recompilation because Mix stores compile config in the Elixir compiler manifest, and equivalent regex literals are not term-equal across evaluations:

~r/foo/ == ~r/foo/
#=> false

If a config file is touched, Mix may re-check compile config and see the newly evaluated regex values as changed even when the config source did not meaningfully change.

This moves the generated live_reload config to runtime.exs under the development environment, preserving behavior while avoiding unstable regex terms in compile config.