SQLite: Don't leak internal schema objects

Related #31201.

If creating custom primary key (like a string) in SQLite, it would also
create an internal index implicitly which named begin with "sqlite_".

It need to be hidden since the internal object names are reserved and
prohibited for public use.

See https://www.sqlite.org/fileformat2.html#intschema

Fixes #33320.

activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb

@@ -7,6 +7,10 @@ module SchemaStatements # :nodoc:
         # Returns an array of indexes for the given table.
         def indexes(table_name)
           exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
+            # Indexes SQLite creates implicitly for internal use start with "sqlite_".
+            # See https://www.sqlite.org/fileformat2.html#intschema
+            next if row["name"].starts_with?("sqlite_")
+
             index_sql = query_value(<<-SQL, "SCHEMA")
               SELECT sql
               FROM sqlite_master
@@ -40,7 +44,7 @@ def indexes(table_name)
               where: where,
               orders: orders
             )
-          end
+          end.compact
         end
 
         def create_schema_dumper(options)

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -457,9 +457,6 @@ def copy_table(from, to, options = {})
         def copy_table_indexes(from, to, rename = {})
           indexes(from).each do |index|
             name = index.name
-            # indexes sqlite creates for internal use start with `sqlite_` and
-            # don't need to be copied
-            next if name.starts_with?("sqlite_")
             if to == "a#{from}"
               name = "t#{name}"
             elsif from == "a#{to}"

activerecord/test/cases/primary_keys_test.rb

@@ -305,6 +305,7 @@ def test_any_type_primary_key
   test "schema dump primary key includes type and options" do
     schema = dump_table_schema "barcodes"
     assert_match %r{create_table "barcodes", primary_key: "code", id: :string, limit: 42}, schema
+    assert_no_match %r{t\.index \["code"\]}, schema
   end
 
   if current_adapter?(:Mysql2Adapter) && subsecond_precision_supported?