feat(core): add AccountIdEndpointMode config option

[siddsriv]

Issue

Internal JS-4633 Part 3

Description

Adds support for AccountIdEndpointMode config option. (client config, env, config file)

Testing

• [x] Unit tests
• [x] Generate the option in ClientInputEndpointParameters example:

  export interface ClientInputEndpointParameters {
  region?: string | Provider<string>;
  useDualstackEndpoint?: boolean | Provider<boolean>;
  useFipsEndpoint?: boolean | Provider<boolean>;
  endpoint?: string | Provider<string> | Endpoint | Provider<Endpoint> | EndpointV2 | Provider<EndpointV2>;
  accountId?: string | Provider<string>;
  accountIdEndpointMode?: string | Provider<string>;
  }

(this is before the merging of https://github.com/aws/aws-sdk-js-v3/pull/6035 which is why accountId is generated as well)

• [x] Generate the option in runtimeConfig.ts example:

  export const getRuntimeConfig = (config: DynamoDBClientConfig) => {
  .
  .
  return {
  ...clientSharedValues,
  ...config,
  runtime: "node",
  defaultsMode,
  accountIdEndpointMode:
    config?.accountIdEndpointMode ?? loadNodeConfig(NODE_ACCOUNT_ID_ENDPOINT_MODE_CONFIG_OPTIONS),
  bodyLengthChecker: config?.bodyLengthChecker ?? calculateBodyLength,

• [x] Generate the option in runtimeConfig.browser.ts example:

  export const getRuntimeConfig = (config: DynamoDBClientConfig) => {
  .
  .
  return {
  ...clientSharedValues,
  ...config,
  runtime: "browser",
  defaultsMode,
  accountIdEndpointMode: config?.accountIdEndpointMode ?? (() => Promise.resolve(DEFAULT_ACCOUNT_ID_ENDPOINT_MODE)),
  bodyLengthChecker: config?.bodyLengthChecker ?? calculateBodyLength,

Checklist

• [x] refactor for core/submodules
• [x] If adding new public functions, did you add the @public tag and enable doc generation on the package?

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[siddsriv]

possibly requires a careful look: exporting from account-id-endpoints submodule especially for config options since they will be used during runtime. the exports for this dir in package.json look right to me, let me know if i missed anything -- all tests are working okay, though it's a little tough to fully test the new client config option's functioning during runtime. i manually confirmed that everything is being imported correctly and the loading statements are correct in the generated client.