**Apache Airflow version**: 1.10.8 (Patched with latest AWS Hook)

**Environment**:

- **Cloud provider or hardware configuration**: 4 VCPU 8GB RAM VM
- **OS** (e.g. from /etc/os-release): RHEL 7.7
- **Kernel** (e.g. `uname -a`): Linux 3.10.0-957.el7.x86_64
- **Install tools**:
- **Others**:
The AWS Hook functionality for AssumeRoleWithSAML is not available in this version, we manually added it via patching the hook file.

**What happened**:
We've been using this hook for a while now with this issue, basically sts.assume_role and sts.assume_role_with_saml will return temporary credentials that are only valid for eg 1 hour by default. Eventually with long running operators / hooks / sensors some of them fail because the credentials have expired.

Example error messages
An error occurred (ExpiredTokenException) when calling the AssumeRole operation: Response has expired
An error occurred (ExpiredTokenException) when calling the AssumeRoleWithSAML operation: Response has expired
botocore.exceptions.ClientError: An error occurred (ExpiredTokenException) when calling the <any operation here> operation: The security token included in the request is expired

**What you expected to happen**:

AWS hook should be updated to use boto3 RefreshableCredentials when temporary credentials are in use.

**How to reproduce it**:

Use any of the assume role methods with the AWS Hook, create a session, wait 1 hour (or whatever expiry period applies to your role), and try and use the hook again.

**Anything else we need to know**:

I have a solution, please self-assign this.
airflow/providers/amazon/aws/hooks/base_aws.py
aws_access_key_id, aws_secret_access_key = self._read_credentials_from_connection()
        aws_session_token = self.extra_config.get("aws_session_token")
        region_name = self.region_name
        if self.region_name is None and 'region_name' in self.extra_config:
            self.log.info("Retrieving region_name from Connection.extra_config['region_name']")
            region_name = self.extra_config["region_name"]
        self.log.info(
            "Creating session with aws_access_key_id=%s region_name=%s",
            aws_access_key_id,
            region_name,
        )
        return boto3.session.Session(
            aws_access_key_id=aws_access_key_id,
            aws_secret_access_key=aws_secret_access_key,
            region_name=region_name,
            aws_session_token=aws_session_token,
            **session_kwargs,
        )
    def _impersonate_to_role(