Migrate ec2inventory plugin to use boto3

[Migrated]

The upgrade to Boto3 is part of an ongoing initiative of having a single instance which coordinates deployments - with support for automatic deployments in pre-production environments.

Boto3 has built-in support for the default AWS Credentials Providers stack.

We need to set the cross-account trusting policies for our accounts, being then able to specify automatic role assumption in a cross-account context via ~/.aws/config.

It might now work out of the box, as it doesn't for aws-cli (see: https://github.com/aws/aws-cli/issues/1604 and https://github.com/aws/aws-cli/issues/1390).
In that case, we would need to do programatic role assumption - I was not been able to fully test this yet (permissions).

Note
This change is intended to be backward-compatible with the current setup - in other words, temporary/static credentials should work as before.

Localisez d’abord le plugin ec2inventory et retracez sa gestion actuelle des identifiants AWS. Vérifiez si le fournisseur d’identifiants par défaut de boto3 prend en charge la configuration intercomptes indiquée, puis évaluez l’assumption programmatique de rôle si nécessaire ; le travail est terminé lorsque la compatibilité avec les identifiants temporaires/statiques est préservée tout en permettant la configuration prévue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.