Loader.GetSourceMigrations() could take SourceMigrationFilters parameter

[lukaszbudnik]

Coordinator.GetSourceMigrations(*SourceMigrationFilters) operation accepts optional filters inSourceMigrationFilters struct.

Under the hood it is implemented as getting all source migrations from and then filtering them:

func (c *coordinator) GetSourceMigrations(filters *SourceMigrationFilters) []types.Migration {
	allSourceMigrations := c.loader.GetSourceMigrations()
	filteredMigrations := c.filterMigrations(allSourceMigrations, filters)
	return filteredMigrations
}

The implementation could be improved and the specific loader (disk, AWS S3, Azure Blob Storage) could accept*SourceMigrationFilters and return already filtered results - better performance and faster operation.