tests/qtest/migration: Split precopy tests

Split the precopy tests from migration-test.c. This is the largest
group of tests and the more difficult one to break into smaller
groups, so move all of it.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

tests/qtest/meson.build

@@ -339,6 +339,7 @@ migration_files = [files(
   'migration/migration-util.c',
   'migration/compression-tests.c',
   'migration/file-tests.c',
+  'migration/precopy-tests.c',
   'migration/postcopy-tests.c',
 )]
 

tests/qtest/migration/framework.h

@@ -223,5 +223,6 @@ static inline void migration_test_add_tls(MigrationTestEnv *env) {};
 void migration_test_add_compression(MigrationTestEnv *env);
 void migration_test_add_postcopy(MigrationTestEnv *env);
 void migration_test_add_file(MigrationTestEnv *env);
+void migration_test_add_precopy(MigrationTestEnv *env);
 
 #endif /* TEST_FRAMEWORK_H */