refactor(providers): convert remaining AWS providers to declarative definitions

Migrate the seven hand-written ServiceProvider subclasses (CloudFormation,
DynamoDB, IAM, Lambda, SNS, SQS, Step Functions) to declarative
ServiceDefinitions executed by the engine, and delete the now-orphaned client
wrappers. IMPERATIVE_PROVIDERS is now an empty (documented) escape hatch.

Add a `list` detail-spec to the declarative engine/types so variable-length
sections (DynamoDB attributes/key schema, CloudFormation parameters/outputs)
can be expressed declaratively — the one capability the FieldSpec model
previously lacked.

Behavior preserved incl. CFN mapping (SQS queue-URL split, Lambda type-prefixed
names, States still unmapped) and metamodel op maps. Two intentional
normalizations to match existing declarative providers: no redundant
"Resource Type" row, and missing values render as "" rather than "N/A".

Add engine list-spec tests and a batch2 provider test suite.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: peter-smith-phd