Unable to connect to KMS encrypted session when using credential_process in .aws/config

I'd really appreciate your help to find the root cause for a problem authenticating sessions when using session-manager-plugin in combination with KMS session encryption and an external credential_process.

**Steps to Reproduce**
1. Windows using latest aws-cli and session-manager-plugin
2. Use a credential process such as [aws-sso-cli](https://github.com/synfinatic/aws-sso-cli) to create authentication profiles in the format:

```
[profile myprofile]
credential_process = c:\aws-sso-cli\aws-sso-cli.exe -u open-url-in-container -S "Default" process --arn arn:aws:iam::123456789:role/myrole
region = us-east-1
```

3. Launch an aws ssm session: `aws ssm start-session --profile myprofile --target mi-1234567890abcd`
4. Observe an error when session-manager-plugin attempts to call KMS after starting the session:

```
Starting session with SessionId: myuser@mydomain.com-1234567890abcdef
Level=fatal msg="'\"Default\"' is not a valid AWS SSO Instance\"

SessionId: myuser@mydomain.com-1234567890abcdef :
----------ERROR-------
Encountered error while initiating handshake. KMSEncryption failed on client with status 2 error: Failed to process activation KMSEncryption: Error calling KMS GenerateDataKey API: ProcessProvider ExecutionError: error in credential_process caused by: exit status 1
```

**Workarounds**
- Hand-edit .aws/config to remove the quotes from the session profile credential_process entry
- Regresses when aws-sso automatically regenerates the config file when user profile assignments are refreshed
- Removing KMS encyrption avoids the error and the SSM session is able to connect
- Non-compliant with corporate security policy

**Thoughts on Problem**
- This problem doesn't appear when using any aws cli command directly: the main aws cli passes the arguments to the credential_process without any modification and it works. That includes calls to "aws ssm" such as starting the PortForwarding document. Hence raising against the session-manager-plugin as the only component affected by the problem
- Something is escaping quotes present in the .aws/config before calling the credential_process, which means the credential_process receives `\"Default\"` instead of `"Default"`, and has no profile named `\"Default\"` causing the failure