feat(lib-dynamodb): expose transact write item types

[lucianlature-endava]

Issue

#7830

Description

Exposes document-client types for TransactWriteItems so consumers can type transaction items instead of using inline shapes.

Changes:

• Codegen: Updated DocumentClientCommandGenerator.java to handle the TransactWriteItems operation.
• New types: TransactWriteConditionCheck, TransactWritePut, TransactWriteDelete, TransactWriteUpdate, and TransactWriteItem.
• Input type: TransactWriteCommandInput now uses TransactWriteItem[] for TransactItems instead of an inline type.
• These types use NativeAttributeValue instead of AttributeValue, matching the document client’s native JS API.

Testing

1. Type-check: cd lib/lib-dynamodb && yarn build:types
2. Unit tests: cd lib/lib-dynamodb && yarn test

Checklist

• If the PR is a feature, add integration tests (*.integ.spec.ts) or E2E tests.
• It's not a feature.
• My E2E tests are resilient to concurrent i/o.
• I didn't write any E2E tests.
• I added access level annotations e.g. @public, @internal tags and enabled doc generation on the package. Remember that access level annotations go below the description, not above.
• I didn't add any public functions.
• Streams - how do they work?? My WebStream readers/locks are properly lifecycled. Node.js stream backpressure is handled. Error handling.
• No streams here.

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[kuhe]

why not just use the type BatchExecuteStatementCommandInput["Statements"]?

[lucianlature-endava]

That would hit a self-reference: BatchExecuteStatementCommandInput["Statements"] will expand to "the type of the Statements property on BatchExecuteStatementCommandInput". But BatchExecuteStatementCommandInput itself is currently being defined, and its Statements property’s type is exactly what we’re trying to specify, so we'll end up with a circular definition, and TypeScript generally can't resolve that as a meaningful alias.

A non-circular DRY version would look like:

export type BatchExecuteStatementStatements = BatchExecuteStatementBatchStatementRequest[] | undefined;
export type BatchExecuteStatementCommandInput = Omit<__BatchExecuteStatementCommandInput, "Statements"> & {
  Statements: BatchExecuteStatementStatements;