swift234

PassManager: Reset state and remove all currently owned transformations

In the current setup analysis information is not reused by new pass managers.
There is no point in having different pass managers. Instead, we can just remove
transformations, reset the internal state of the pass manager, and add new
transformation passes. Analysis information can be reused.

Reuse one pass manager in the pass pipeline so that we don't have to
unnecessarily recompute analysis information.

Swift SVN r19917