Identified with misc-include-cleaner.

This pass isn't used anywhere upstream and thus has no test coverage.
For these reasons, remove it.

This pass isn't used anywhere upstream and thus has no test coverage.
For these reasons, remove it.

This pass isn't used upstream anywhere and doesn't have have a
create...() function, thus isn't tested anywhere. Because of this,
remove it.

UnifyFunctionExitNodesLegacyPass isn't used anywhere in upstream and
thus isn't tested at all. For these reasons, remove it.

The last use was removed by:

  commit ae0987d242e266847f21f5fa1bffa97ce3eff586
  Author: Kazu Hirata <kazu@google.com>
  Date:   Sat Jun 10 13:51:35 2023 -0700

Differential Revision: https://reviews.llvm.org/D152636

A new attempt after removing uses of -instnamer in polly lit tests
in D148530.

This reverts commit 981ec1faeb508a364cc47c8246b72fc89dd8c1d8.

It broke polly build bots. Polly still uses -instnamer with legacy PM.