Support apply smart case to each individual search pattern separately

[xaljer]

Describe your feature request

ripgrep support to search several patterns together by -e or listing patterns in a file and using -f to specify the file.
Meanwhile, --smart-case option can judge search pattern if it needs a case sensitive searching. But, for now, all patterns are treated together to match the smart case rule. i.e. if I use rg -S -e Abc -e bcd, search pattern bcd also be treated as case sensitive.
So, I think it's better to support apply smart case rule to every search pattern separately, especially in the -f usage. But I am not sure if patterns in a single regex should support this.

I think ripgrep's man page for this change would be like:

 -S, --smart-case
            Searches case insensitively if the pattern is all lowercase. Search case
            sensitively otherwise. Every individual search pattern follow this rule 
            by itself, including PATTERN specified by -e and patterns in PATTERNFILE
            specified by -f.

[FinnRG]

The case-insensitive flag also behaves like that. Should this be changed for every flag?

[BurntSushi]

The -i flag does not behave like this. The key here is that -S has to actually look at the pattern to determine whether to enable the mode or not. -i does not, as it is unconditional.