codeartifact login should pick appropriate environment

### Describe the feature

Running
```bash
aws codeartifact login --tool pip ...
```
updates the user’s `pip` configuration instead of the virtual environment’s if run inside a venv which doesn’t already have a configuration. (Bug?) The [`pip` documentation](https://pip.pypa.io/en/latest/cli/pip_config/) states

> If none of --user, --global and --site are passed, a virtual environment configuration file is used if one is active and the file exists. Otherwise, all modifications happen to the user file by default.

Note the “if … the file exists”. Looking at the code

https://github.com/aws/aws-cli/blob/88e8fabe20b18cd83c72955c0fb547ad35ffa55b/awscli/customizations/codeartifact/login.py#L382

none of these three options are passed. That behavior is actually pretty annoying because _every other_ venv on my machine can then inherit that artifactory which was meant for just one venv.

**Proposal**: Either be more careful checking for an activated virtual environment by checking for [`VIRTUAL_ENV`](https://docs.python.org/3/library/venv.html) or give the user an option so she can select one of the three `pip` options.

### Use Case

See above: running `aws codertifact login --tool pip ...` can quickly set the user’s `pip` configuration and ignores an activated venv. That’s created quite a mess for me across venvs.

### Proposed Solution

Replace

https://github.com/aws/aws-cli/blob/88e8fabe20b18cd83c72955c0fb547ad35ffa55b/awscli/customizations/codeartifact/login.py#L382

with something like
```python
if "VIRTUAL_ENV" in os.environ:
return [['pip', 'config', '--site', 'set', 'global.index-url', pip_index_url]]
return [['pip', 'config', 'set', 'global.index-url', pip_index_url]]
```
or
```python
if "VIRTUAL_ENV" in os.environ:
pip_conf = os.path.join(os.environ["VIRTUAL_ENV"], "pip.conf")
if not os.path.isfile(pip_conf):
open(pip_conf, "a").close()
return [['pip', 'config', 'set', 'global.index-url', pip_index_url]]
```
or some such. Alternatively, add a command-line option to `aws codeartifactory login` (e.g. `--pip-conf`) which allows the `aws` user to pass one of the three `pip` options.

### Other Information

To deal with the issue, I had to run the following commands after `aws`:
```bash
pip config debug
pip config --site set global.index-url `pip config get global.index-url`
pip config --user unset global.index-url
```
In the future, running
```bash
touch "${VIRTUAL_ENV}/pip.conf"
```
before `aws` also seems to work.

### Acknowledgements

- [X] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CLI version used

aws-cli/2.7.8 Python/3.9.13 Darwin/18.7.0 source/x86_64 prompt/off

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

macOS Darwin 18.7.0 Darwin Kernel Version 18.7.0, Mojave 10.14.6