Fix Hashicorp client authentication for userpass and aws_iam methods

[hussein-awala]

closes: #31573

In hvac 0.7.0, all auth method classes were moved under the auth property on the hvac.Client class, and the old methods were deprecated and removed in the version 1.0.0.
In this PR I switch to the new methods for the last two authentication methods which are on the old ones: userpass and aws_iam.

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[ashb]

What min version of hvac do we depend on? Do we need to bump that version, or is the min requirement already high enough?

I'm approving on the grounds that you've checked this and we're good with the min already.

[hussein-awala]

What min version of hvac do we depend on? Do we need to bump that version, or is the min requirement already high enough?
I'm approving on the grounds that you've checked this and we're good with the min already.

@ashb yes I already checked it, the min version of hvac is 0.10 which is high enough for this change.

airflow/generated/provider_dependencies.json

Line 463 in ec18db1

"hvac>=0.10"