Docs: add instructions in ops.md + simplify backend csv

[am17an]

1. Removed various transient things like commit, test_time etc. to simplify the csv files so now when someone adds we are able to see the diff instead of the entire file changing.

2. Added instructions in docs/ops.md on how to add new backends. It will help if others contributed, we only have 4 backends here at the moment

3. docs/ops.md update

[CISC]

I was looking into updating this table the other day, but the massive CSV diffs were really offputting, this is so much better! :)

[slaren]

It would be nice if the commit (and other details) could still be included, maybe by using a more flexible format like JSON so that it only needs to be written once, but this is already an improvement.

[CISC]

cc/ @0cc4m @qnixsynapse @lhez @hipudding

[0cc4m]

Done in #14900 @CISC, thanks for the reminder.

[qnixsynapse]

Opened #14901 .. Thank you! @CISC

[CISC]

@ggerganov Metal needs a refresh to remove RMS_NORM_MUL from the table.

[lhez]

@CISC done in #14910, thank you for the reminder!

[hipudding]

@CISC Thanks. Will add ops list in #14935