77087 Enable file_names and package_names lints (a: accessibility, cla: yes, framework, team, waiting for tree to go green)

77090 Add instructions to integration_test example README (a: tests, cla: yes, framework, waiting for tree to go green)

77093 Apply changes caused by https://github.com/flutter/flutter/pull/76662 (cla: yes, d: examples, team, waiting for tree to go green)

77095 Enable null_closures (cla: yes, team, waiting for tree to go green)

77098 Clean-up analysis_options files (a: internationalization, a: tests, cla: yes, d: examples, framework, team, waiting for tree to go green)