feat(middleware-stack): add filter() function to middleware stack

[AllanZhengYP]

Issue #, if available:

Description of changes:
Add a filter function to middleware stack class. This enables you to make copy of middleware stack with specific stats(priority, step, tags).

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[AllanZhengYP]

As a note here: the filter() is available in the @aws-sdk/middleware-stack's middleware stack interface but not not available in generalized @aws-sdk/types's middleware stack. Because filter() depends some members that only available in the former class implementation but not in the generalized interface.

[lock]

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