[Bug] leaderboard would fetch data 2 times and it's inefficient

[timelessnesses]

Describe the bug
every leaderboard command always fetch 10 guilds data first then fetch all of them might cause memory leaks

To Reproduce
nah

Expected behavior
Should've been a feature to either limit or ordering correctly

Screenshots
no
Bot information:

• Discord.py commit (check with python -m discord -v):

- Python v3.10.6-final
- discord.py v2.3.0-alpha
    - discord.py metadata: v2.3.0a4848+gd34a8841
- aiohttp v3.8.4
- system info: Linux 5.15.0-75-generic #82-Ubuntu SMP Tue Jun 6 23:10:23 UTC 2023

• Bot's commit (check with git rev-parse --short HEAD): 89d9366

Additional context
implement nicer way to get lb