Not able to changes default account id (000000000000) of cdklocal.

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I tried:

1. I have tried adding export CDK_DEFAULT_ACCOUNT, but it did not picking up the account from the env, it still points to 000000000000.

2. I was able to change the default region by doing aws configure, cdklocal synth --profile localstack, but aws configure doesn't accept account id.

Why I want to change default account id. we have account specific context in cdk.json, when we run cdklocal synth it's try to pickup account specifc context based on account id.

cdk.json:

{
"context": {
"account-id": {
"bucket-name": "test-dev"
},
"account-id2": {
"bucket-name": "test-dev"
}
}
}

app.py:

context = app.node.try_get_context(os.environ["CDK_DEFAULT_ACCOUNT"])

Reproduce the report with `cdklocal synth --profile localstack`, then inspect the `cdk.json` context and the `app.py` lookup using `CDK_DEFAULT_ACCOUNT`. Confirm whether the account-specific context is selected from the environment or remains `000000000000`; done means the requested account id selects the corresponding context.

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