Add script to refresh migrations timestamps

What does this MR do and why?

Add script to refresh migrations timestamps

Usage:

• ./scripts/refresh-migration-timestamps - updates the timestamps to a value starting from now.
• ./scripts/refresh-migration-timestamps --after 'a week from tomorrow' - regenerates the timestamps to start from a week from the moment of execution. This uses Chronic to parse the expression.

This is useful for reordering migrations when they depend on a different merge request and as an easier alternative to https://docs.gitlab.com/ee/development/migration_style_guide.html#migration-timestamp-age

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

With new migrations:

marius@rocket-sled ~/W/g/gitlab (mb-refresh-migration-timestamp)> rails g post_deployment_migration partition_ci_pipelines_config_table
      create  db/post_migrate/20240904104311_partition_ci_pipelines_config_table.rb
marius@rocket-sled ~/W/g/gitlab (mb-refresh-migration-timestamp)> ./scripts/refresh-migration-timestamps --after 'a week from tomorrow'
$ git ls-files --others --exclude-standard -- db/migrate db/post_migrate
db/post_migrate/20240904104311_partition_ci_pipelines_config_table.rb

$ git merge-base master HEAD
275a56e8bbbeb113dffa546f601f9e953758c5e3

$ git diff --name-only --diff-filter=A 275a56e8bbbeb113dffa546f601f9e953758c5e3 -- db/migrate db/post_migrate

$ mv db/post_migrate/20240904104311_partition_ci_pipelines_config_table.rb db/post_migrate/20240912090004_partition_ci_pipelines_config_table.rb
$ ./scripts/regenerate-schema
# output from regenerate schema

With existing migrations

marius@rocket-sled ~/W/g/gitlab (469056-partition-ci_pipelines_config)> ./scripts/refresh-migration-timestamps --after 'a week from tomorrow'
$ git ls-files --others --exclude-standard -- db/migrate db/post_migrate

$ git merge-base master HEAD
275a56e8bbbeb113dffa546f601f9e953758c5e3

$ git diff --name-only --diff-filter=A 275a56e8bbbeb113dffa546f601f9e953758c5e3 -- db/migrate db/post_migrate
db/migrate/20240903073815_create_p_ci_pipelines_config.rb
db/post_migrate/20240903074608_fk_ci_pipelines_config_ci_pipelines.rb
db/post_migrate/20240903074926_partition_ci_pipelines_config.rb

$ mv db/migrate/20240903073815_create_p_ci_pipelines_config.rb db/migrate/20240912090005_create_p_ci_pipelines_config.rb
$ mv db/post_migrate/20240903074608_fk_ci_pipelines_config_ci_pipelines.rb db/post_migrate/20240912090009_fk_ci_pipelines_config_ci_pipelines.rb
$ mv db/post_migrate/20240903074926_partition_ci_pipelines_config.rb db/post_migrate/20240912090012_partition_ci_pipelines_config.rb
$ ./scripts/regenerate-schema
# output from regenerate schema