common: migrate the deprecated --mmap/--no-mmap to --load-mode (#26934)

Replace the deprecated --mmap, --no-mmap, --mlock, and --direct-io flags with
the unified --load-mode argument across scripts, examples, and documentation.
Internal warning message and env var docs updated accordingly.

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>

scripts/snapdragon/adb/run-completion.sh

@@ -79,7 +79,7 @@ adb $adbserial $adbhost shell " \
     LD_LIBRARY_PATH=$basedir/$branch/lib   \
     ADSP_LIBRARY_PATH=$basedir/$branch/lib \
     $verbose $sched $opmask $profile $nhvx $hmx $ndev $hb $opbatch $opqueue $oppoll $opflt $opfuse $vmem $mbuf $mmsel $fasel \
-      ./$branch/bin/llama-completion --no-mmap -m $basedir/../gguf/$model \
+      ./$branch/bin/llama-completion --load-mode none -m $basedir/../gguf/$model \
          --poll 1000 -t 6 --cpu-mask 0xfc --cpu-strict 1                  \
          --ctx-size 8192 --ubatch-size 1024 -fa on                        \
          -ngl 99 --device $device $cli_opts $@                            \