BM_ShellInitializationAndShutdown has a wrong measurement

[liyuqian]

After flutter/engine@42b40b4, the BM_ShellInitializationAndShutdown benchmark dropped down significantly because we no longer measure the font manager setup time.

Although the setup is no longer a part of startup or shutdown, if the benchmark is measuring the complete time from startup to shutdown, it should still be included.

[github-actions]

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