[lldb/Commands] Fix short option collision for `process launch`

This patch changes the short option used in `CommandOptionsProcessLaunch`
for the `-v|--environment` command option to `-E|--environment`.

The reason for that is, that it collides with the `-v|--structured-data-value`
command option generated by `OptionGroupPythonClassWithDict` that
I'm using in an upcoming patch for the `process launch` command.

The long option `--environment` remains the same.

Differential Review: https://reviews.llvm.org/D95100



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>