Add configurable timeout for execute-app-function

The `execute-app-function` command had a hardcoded 10-second timeout, which was insufficient for longer-running functions. This resulted in premature timeouts
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Introduces a `--timeout-duration` flag for specifying a custom timeout and increases the default timeout to 30 seconds.

Bug: b/433529739 & b/418719120
Test: Manually tested the new flag and default timeout.
Flag: EXEMPT Tooling change for shell command output.
Change-Id: Id8e7a875e8540ead2034e288cb776c36ebe3736a