maxSigtermDelay is configured with wrong type when transformed to environment variable.

[mlallaouret]

Expected Behavior

maxSigtermDelay should be pass as a duration to the cloud sql proxy container to be taken into account

Actual Behavior

maxSigtermDelay is configured as an environment variable with a number value type whereas the cloud sql proxy expects a duration (https://github.com/GoogleCloudPlatform/cloud-sql-proxy/blob/a2070bf1c6be9996945229b1b1e0a98ce9b36dd5/cmd/root.go#L468)
A number without unit is considered as 0 for a duration (tested here: https://pkg.go.dev/time#ParseDuration).

Steps to Reproduce the Problem

n/a

Specifications

• Version: 1.4.3
• Platform: GKE

I will propose a pull request to resolve this issue.