Testing: GetDurableExecution ignores the function qualifier in FunctionArn and Version

[yaythomas]

Where

packages/aws-durable-execution-sdk-python-testing, Executor.get_execution (executor.py).

What happens

GetDurableExecution builds FunctionArn as arn:aws:lambda:<region>:<account>:function:<name> from the start input's function name alone, and returns Version: "1.0" fixed.

So an execution started for child:prod reports:

FunctionArn=arn:aws:lambda:eu-west-1:999999999999:function:child
Version=1.0

The service returns the function ARN with the qualifier the execution was started with, and the version of the function that ran ($LATEST or a version number).

Where it shows

• A chained invoke of a qualified target (context.invoke("child:prod", ...)) creates a child execution; its GetDurableExecution drops the qualifier. This is the visible case since Add chained invoke to the local runner #731 added chained invokes.
• A root execution started with a qualifier has the same gap; that predates Add chained invoke to the local runner #731.

Proposed change

• Build FunctionArn from the start input's function name and qualifier when a qualifier is present.
• Report the qualifier as Version when it is a version number, else $LATEST. An alias's target version is not known locally, so an alias reports $LATEST.
• Tests: bare and qualified targets, root and child executions.

Found in review of #731; filed as a follow-up so that PR stays scoped to the chained-invoke operation.