fix: strengthen types, simplify logic

[obataku]

what

• enable & use optional attributes where AWS API marks fields optional
• remove redundant lookups
• strengthen types for log_configuration, repository_credentials, system_controls, container_definition
• reorder object var attributes to match AWS docs
• simplify log configuration sanitization/munging
• simplify secret & environment var sorting
• expose unencoded container definition output directly without requiring pointless jsonencode/jsondecode cycle

why

• optional obviates lookup(..., null) calls for objects
• lookup(o, k) without a default is deprecated in favor of o[k] or direct attr access (o.k)
• log_configuration, repository_credentials, and system_controls had needlessly opaque any types which hinder DX and make subtle bugs more likely (e.g. in the types of log_configuration.options values)
• since all attributes of container_definition are now typed there's no reason not to type it as well
• following the AWS documentation's field order makes types easier to verify for completeness & correctness
• typing log_configuration appropriately obviates explicit tostring & null handling; resolves #151
• env/secret map sorting can be dramatically simplified since for-expressions iterate over maps & objects by key in lexicographic order
• jsonencode-ing the final container definition only to jsondecode for json_map_object is redundant

[Gowiem]

@obataku can you get back to Nitro's requested changes and deal with the branch conflicts that you have? And if no longer relevant, feel free to close out. Thanks!

[goruha]

/terratest

[goruha]

@obataku Thanks for your contribution.

I merged your PR into the feature branch to polish the code, fix conflicts and will merge it into the main branch and cut new release