AWS CLI slow startup

### Describe the bug

AWS CLI is three times as slow as s3cmd when tested on a local S3 implementation. s3fs-fuse invokes AWS CLI hundreds of times so this slows down integration tests. I tested on an Intel i7-1250U. I previously reported these symptoms in #6500.

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Expected Behavior

```
$ time s3cmd ls s3://

real 0m0.091s
user 0m0.073s
sys 0m0.016s
```

### Current Behavior

```
$ time AWS_EC2_METADATA_DISABLED=true aws s3 ls --region us-east-1 --endpoint-url http://127.0.0.1:8081 --profile s3proxy

real 0m0.346s
user 0m0.284s
sys 0m0.055s
```

### Reproduction Steps

See above

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CLI version used

aws-cli/2.17.18 Python/3.13.0 Linux/6.11.4-300.fc41.x86_64 source/x86_64.fedora.41

### Environment details (OS name and version, etc.)

Fedora 41