InstancePool: min-available support

[tgrondier]

Description

Under the hood this is a full port of instancepool management and commands from egoscale v2 to egoscale v3!

Checklist

(For exoscale contributors)

• Changelog updated (under Unreleased block)
• Acceptance tests OK
• For a new resource, datasource or new attributes: acceptance test added/updated

Testing

Acceptance tests:

TF_ACC=1 /usr/local/go/bin/go test                      \
        -race                   \
        -timeout=90m            \
        -tags=testacc           \
        -v -parallel=3 -count=1 -failfast   \
        github.com/exoscale/terraform-provider-exoscale/pkg/resources/instance_pool
=== RUN   TestInstancePool
=== RUN   TestInstancePool/DataSource
=== RUN   TestInstancePool/DataSourceList
=== RUN   TestInstancePool/Resource
--- PASS: TestInstancePool (167.55s)
    --- PASS: TestInstancePool/DataSource (57.13s)
    --- PASS: TestInstancePool/DataSourceList (41.89s)
    --- PASS: TestInstancePool/Resource (68.53s)
PASS
ok      github.com/exoscale/terraform-provider-exoscale/pkg/resources/instance_pool     168.582s