build: drop unused feature macros, update exception list

- cmp-config.pl: add remaining exceptions. Sort list.

- drop unused `HAVE_SYS_WAIT_H`.
  Follow-up to 50def7c881 #13249

- drop unused `HAVE_FCHMOD`.
  Follow-up to 03cb1ff4d6 #12395

- autotools: stop promoting variables to macros:
  `USE_NGTCP2_CRYPTO_*`, `USE_NGTCP2_H3`, `USE_OPENSSL_H3`,
  `HAVE_LIBRESSL`.
  They are not used in the source.

- cmake: drop unused `HAVE_O_NONBLOCK`,
  `HAVE_DISABLED_NONBLOCKING`.

- lib: drop `NEED_MALLOC_H`.
  It was used in manual-build cases for Amiga/MS-DOS/Windows/WinCE, but
  never by autotools/cmake, thus apparently unnecessary.

- lib: drop unused `NEED_MEMORY_H`.

- lib: simplify classic mac feature guards,
  drop `HAVE_EXTRA_STRICMP_H` and `HAVE_EXTRA_STRDUP_H`.

- autotools: drop unused `HAVE_GETHOSTBYNAME` detection.

- autotools: drop unused OpenSSL feature tests:
  `HAVE_ERR_H`, `HAVE_PEM_H`, `HAVE_RSA_H`

- autotools: drop unused OpenSSL feature tests:
  `HAVE_X509_H`, `HAVE_CRYPTO_H`, `HAVE_SSL_H`.

  They performed a fallback check when the primary check missed
  `openssl/x509.h`. Though if any other prefixed headers were found,
  OpenSSL is already assumed detected.

  The fallback check was looking for 3 unprefixed OpenSSL headers, and
  if all found, marked OpenSSL found internally, but did not promote
  it to `curl_config.h` via `USE_OPENSSL`. Meaning it either didn't do
  anything or may have continued with an inconsistent state.
  Added in d99c20f628 (2008)

  At the time, there was an extra `AC_DEFINE(USE_SSLEAY, 1 ...` logic
  after this code, which kicked in in the fallback case, but that code
  was deleted in 709cf76f6b (2015)

  Follow-up to 709cf76f6b

- autotools: drop `AC_SUBST()` where the value is explicitly set anyway
  and the macro is unused.

- autotools: replace `AC_SUBST(VAR, 1)` with local variable assigments,
  where the `@VAR@` macro is unused. Also dedupe the local variable if
  there was a parallel one used for the same purpose.

- autotools: drop local feature variables that were never used.

- autotools: drop unused `CURL_CHECK_OPTION_NTLM_WB`,
  `CURL_CHECK_NTLM_WB`.
  Also stop setting unused `NTLM_WB_ENABLED` macro for VMS.
  Follow-up to 50def7c881 #13249

- autotools: drop unused `PKGADD_*`.
  Follow-up to bae0d473f5 #3331

- autotools: drop unused `CURL_NETWORK_LIBS`.
  Follow-up to 3af75e18d6 #14697

Closes #15577

m4/curl-rustls.m4

@@ -94,7 +94,6 @@ if test "x$OPT_RUSTLS" != xno; then
         AC_CHECK_LIB(rustls, rustls_connection_read,
           [
           AC_DEFINE(USE_RUSTLS, 1, [if Rustls is enabled])
-          AC_SUBST(USE_RUSTLS, [1])
           RUSTLS_ENABLED=1
           USE_RUSTLS="yes"
           ssl_msg="rustls"
@@ -128,7 +127,6 @@ if test "x$OPT_RUSTLS" != xno; then
       SSL_CPPFLAGS=`CURL_EXPORT_PCDIR([$RUSTLS_PCDIR]) dnl
         $PKGCONFIG --cflags-only-I rustls 2>/dev/null`
 
-      AC_SUBST(SSL_LIBS)
       AC_MSG_NOTICE([pkg-config: SSL_LIBS: "$SSL_LIBS"])
       AC_MSG_NOTICE([pkg-config: SSL_LDFLAGS: "$SSL_LDFLAGS"])
       AC_MSG_NOTICE([pkg-config: SSL_CPPFLAGS: "$SSL_CPPFLAGS"])
@@ -145,7 +143,6 @@ if test "x$OPT_RUSTLS" != xno; then
       link_pkgconfig=1
       ssl_msg="rustls"
       AC_DEFINE(USE_RUSTLS, 1, [if Rustls is enabled])
-      AC_SUBST(USE_RUSTLS, [1])
       USE_RUSTLS="yes"
       RUSTLS_ENABLED=1
       test rustls != "$DEFAULT_SSL_BACKEND" || VALID_DEFAULT_SSL_BACKEND=yes