feat: add support for accountId in imds

[smilkuri]

Issue #, if available:
Internal JS-5966

Description of changes:

This PR adds support for version 2.1 of the IMDS credentials provider. With this update, the provider can now retrieve credentials that include an account ID.

To support this functionality, the credentials provider first attempts to access the extended API endpoint, which ends with -extended. If this endpoint returns a 404, the provider falls back to the legacy API endpoint—the same one used in the IMDS credentials provider v2.0.

This "try extended API, then fall back to legacy API" pattern is applied to both retrieving the IMDS instance profile name and fetching credentials.
Only the extended API can return credentials that include an account ID.

The PR also made the following IMDS credentials providers options configurable:

• Disable IMDS credentials fetching
• IMDS instance profile name

Both options can be configured via environment variables or a shared config file, with environment variables taking precedence over the config file.

ToDo:

• Add support for feature Id tracking

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[kuhe]

this is hard to understand because the mock is too broad. What config property is being targeted by this mock return value?

Can the mock be made more specific so we can tell what config property it is trying to intercept?

[kuhe]

• create e2e test suite runnable in an EC2 instance. Extra testing is important for credentials-related code

[kuhe]

comments for the PR as of June 26:

• variable names need to differentiate "AWS_PROFILE" init.profile, "imdsProfile", and "ec2InstanceProfile". How do these conceptually relate to each other? Are profile and imds profile separate? Is ec2InstanceProfile a subset of imdsProfile?
• I updated the PR to not use positional arguments. There were too many redundancies between elements of the RemoteProviderInit and positional args like maxRetries, logger, "profile" etc. and the use of "profile" as an argument name was too ambiguous.
• more tests are needed to cover variations in inputs/config

[kuhe]

the PR is on hold