use SQL's limit/offset pagination for nextIndex/maxCount requests (#185)

Instead of retrieving the entire list of items/characters/scores/etc. at once (and even store them in memory), use SQL's `LIMIT ... OFFSET ...` pagination so we only take what we need.

Currently only CHUNITHM uses this, but this will also affect maimai DX and O.N.G.E.K.I. once the PR is ready.

Also snuck in a fix for CHUNITHM/maimai DX's `GetUserRivalMusicApi` to respect the `userRivalMusicLevelList` sent by the client.

### How this works

Say we have a `GetUserCharacterApi` request:

```json
{
    "userId": 10000,
    "maxCount": 700,
    "nextIndex": 0
}
```

Instead of getting the entire character list from the database (which can be very large if the user force unlocked everything), add limit/offset to the query:

```python
select(character)
.where(character.c.user == user_id)
.order_by(character.c.id.asc())
.limit(max_count + 1)
.offset(next_index)
```

The query takes `maxCount + 1` items from the database to determine if there is more items than can be returned:

```python
rows = ...

if len(rows) > max_count:
    # return only max_count rows
    next_index += max_count
else:
    # return everything left
    next_index = -1
```

This has the benefit of not needing to load everything into memory (and also having to store server state, as seen in the [`SCORE_BUFFER` list](2274b42358/titles/chuni/base.py (L13)).)

Reviewed-on: https://gitea.tendokyu.moe/Hay1tsme/artemis/pulls/185
Co-authored-by: beerpsi <beerpsi@duck.com>
Co-committed-by: beerpsi <beerpsi@duck.com>

titles/mai2/schema/profile.py

@@ -1,15 +1,26 @@
-from core.data.schema import BaseData, metadata
-from titles.mai2.const import Mai2Constants
+from datetime import datetime
+from typing import Dict, List, Optional
 from uuid import uuid4
 
-from typing import Optional, Dict, List
-from sqlalchemy import Table, Column, UniqueConstraint, PrimaryKeyConstraint, and_
-from sqlalchemy.types import Integer, String, TIMESTAMP, Boolean, JSON, BigInteger, SmallInteger, VARCHAR, INTEGER
+from sqlalchemy import Column, Table, UniqueConstraint, and_
+from sqlalchemy.dialects.mysql import insert
+from sqlalchemy.engine import Row
 from sqlalchemy.schema import ForeignKey
 from sqlalchemy.sql import func, select
-from sqlalchemy.engine import Row
-from sqlalchemy.dialects.mysql import insert
-from datetime import datetime
+from sqlalchemy.types import (
+    INTEGER,
+    JSON,
+    TIMESTAMP,
+    VARCHAR,
+    BigInteger,
+    Boolean,
+    Integer,
+    SmallInteger,
+    String,
+)
+
+from core.data.schema import BaseData, metadata
+from titles.mai2.const import Mai2Constants
 
 detail = Table(
     "mai2_profile_detail",
@@ -495,7 +506,7 @@ consec_logins = Table(
     mysql_charset="utf8mb4",
 )
 
-rival = Table(
+rival: Table = Table(
     "mai2_user_rival",
     metadata,
     Column("id", Integer, primary_key=True, nullable=False),
@@ -908,8 +919,23 @@ class Mai2ProfileData(BaseData):
         if result:
             return result.fetchall()
 
-    async def get_rivals_game(self, user_id: int) -> Optional[List[Row]]:
-        result = await self.execute(rival.select(and_(rival.c.user == user_id, rival.c.show == True)).limit(3))
+    async def get_rivals_game(
+        self,
+        user_id: int,
+        limit: Optional[int] = None,
+        offset: Optional[int] = None,
+    ) -> Optional[List[Row]]:
+        sql = select(rival).where((rival.c.user == user_id) & rival.c.show.is_(True))
+
+        if limit is not None or offset is not None:
+            sql = sql.order_by(rival.c.id)
+        if limit is not None:
+            sql = sql.limit(limit)
+        if offset is not None:
+            sql = sql.offset(offset)
+
+        result = await self.execute(sql)
+
         if result:
             return result.fetchall()