feat(lib-dynamodb): add support for imprecise numbers and custom number retrieval

[RanVaknin]

Issue

#6571
The SDK was throwing errors when handling large numbers (>MAX_SAFE_INTEGER) that worked in v2. This affected both:

1. Marshalling: marshall({ foo: 1.23e+40 }) would throw an error
2. Unmarshalling: unmarshall({ foo: { N: "1.23e+40" } }) required explicit handling

Description of changes

1. Added marshallOptions.allowImpreciseNumbers

   • When true: Allows storing numbers > MAX_SAFE_INTEGER with potential precision loss (matches v2 behavior)
   • When false (default): Maintains existing precision protection

2. expanded unmarshallOptions.wrapNumbers - Now accepts a function: (value: string) => number | bigint | NumberValue where customers can provide their own custom unmarshalling logic.

3. Added unit test to cover the new marshal option and the expanded unamarshal option

4. Updated @aws-sdk/lib-dynamodb readme docs to reflect the changes.

Driver code setup:

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocumentClient, PutCommand, GetCommand } from "@aws-sdk/lib-dynamodb";

const impreciseClient = DynamoDBDocumentClient.from(new DynamoDBClient({}), {
    marshallOptions: { allowImpreciseNumbers: true }
});

try {
  await impreciseClient.send(new PutCommand({
    TableName: "TestLargeNumbers",
    Item: { 
        id: 123,
        largeNumber: 34567890123456789012345678901234567890 // Store item with number larger than MAX_SAFE_INTEGER 
    }
}));

const result = await impreciseClient.send(new GetCommand({ 
    TableName: "TestLargeNumbers",
    Key: { id: 123 }
}));

console.log(result.Item);

} catch (error) {
  console.log(error);
}

Results in:

{ id: 123, largeNumber: 34567890123456790000000000000000000000n }

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