Fix issue with logger config on Rails boot

[tombruijn]

I'm looking into an issue with the AppSignal logger not logging all the same logs as the Rails logger does itself.

It seems to work better by adding the AppSignal logger config to config/application.rb or one of the environment files, but not without running into the error error first.

Make a quick fix by checking if we can set a formatter on the loggers before configuring one.
This could cause issues with different formats, but at least it won't cause the Rails app to fail to start.

`block in formatter=': undefined method `formatter=' for nil (NoMethodError)

        logger.formatter = formatter
              ^^^^^^^^^^^^
	from /integration/lib/appsignal/logger.rb:96:in `each'
	from /integration/lib/appsignal/logger.rb:96:in `formatter='
	from /app/vendor/bundle/ruby/3.3.0/gems/activesupport-8.0.2/lib/active_support/tagged_logging.rb:132:in `new'
	from /app/config/application.rb:42:in `<class:Application>'
	from /app/config/application.rb:10:in `<module:ExampleApp>'
	from /app/config/application.rb:9:in `<main>'
	from /usr/local/lib/ruby/3.3.0/bundled_gems.rb:69:in `require'
	from /usr/local/lib/ruby/3.3.0/bundled_gems.rb:69:in `block (2 levels) in replace_require'
	from /app/vendor/bundle/ruby/3.3.0/gems/bootsnap-1.18.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/commands/server/server_command.rb:139:in `block in perform'
	from <internal:kernel>:90:in `tap'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/commands/server/server_command.rb:136:in `perform'
	from /app/vendor/bundle/ruby/3.3.0/gems/thor-1.3.2/lib/thor/command.rb:28:in `run'
	from /app/vendor/bundle/ruby/3.3.0/gems/thor-1.3.2/lib/thor/invocation.rb:127:in `invoke_command'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/command/base.rb:178:in `invoke_command'
	from /app/vendor/bundle/ruby/3.3.0/gems/thor-1.3.2/lib/thor.rb:538:in `dispatch'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/command/base.rb:73:in `perform'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/command.rb:65:in `block in invoke'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/command.rb:143:in `with_argv'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/command.rb:63:in `invoke'
	from /app/vendor/bundle/ruby/3.3.0/gems/railties-8.0.2/lib/rails/commands.rb:18:in `<main>'
	from /usr/local/lib/ruby/3.3.0/bundled_gems.rb:69:in `require'
	from /usr/local/lib/ruby/3.3.0/bundled_gems.rb:69:in `block (2 levels) in replace_require'
	from /app/vendor/bundle/ruby/3.3.0/gems/bootsnap-1.18.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
	from bin/rails:4:in `<main>'

[tombruijn]

Build failures are unrelated because they also happen on the main branch.