Added R_Pack04 with exposed pad

This MR adds a (sort of) new symbol for a resistor array with an additional exposed pad. Like the ADI LT5400.

I have added a symbol for both R_Pack04_EP and R_Pack04_EP_Split, which were derived from R_Pack04 and R_Pack04_Split

I placed the EP pin on the side to allow using the array as suggested in the datasheet:

The split symbol adds a new EP unit

I use the split version to implement a Howland current source.

The KLC errors stem from the resistor with their shorted pins.

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