[openssl/openssl] 66f478: Create hierarchical demo Makefile.

[Shane]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 66f4782f1452d6fbfab78822b340a99aaeacc2f0
      https://github.com/openssl/openssl/commit/66f4782f1452d6fbfab78822b340a99aaeacc2f0
  Author: slontis <shane.lontis at oracle.com>
  Date:   2023-10-25 (Wed, 25 Oct 2023)

  Changed paths:
    A demos/Makefile
    M demos/bio/Makefile
    M demos/cipher/Makefile
    M demos/digest/Makefile
    M demos/encode/Makefile
    M demos/encrypt/Makefile
    M demos/kdf/Makefile
    A demos/keyexch/Makefile
    M demos/mac/Makefile
    M demos/pkey/Makefile
    M demos/signature/Makefile
    M demos/sslecho/makefile

  Log Message:
  -----------
  Create hierarchical demo Makefile.

Adds a Makefile with all, clean, and test targets.
This has only been added for demos that already contain Makefiles.
For problematic tests that require inputs, the test target does nothing.

(Note: Demos should be self contained and not require unknown external
inputs. This PR does not attempt to fix this.)

Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Tim Hudson <tjh at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20546)