Deprecate the --source command line option for the package sub-command

[Gedochao]

• the --source command line option alias (which makes the package sub-command produce source JARs) is getting deprecated in preparation for Misc improvements in compiler options handling #3253.
• it will likely be removed in Scala CLI v1.6.0, where --source will be treated as a compiler option instead.
• the recommended syntax would now be --src.

scala-cli-jvm --power package --source .                       
# [warn] The --source option alias has been deprecated and may be removed in a future version.
(...)

[tgodzik]

LGTM

[SethTisue]

I'm sorry, I know this feedback is coming too late, but could a more different name than --src be found? --src and -source still seem awfully confusable with each other, especially when spoken out loud.

[SethTisue]

Maybe --with-sources?

[tgodzik]

--src already existed before and I agree it's easy to confuse. @Gedochao maybe we should deprecate both?