fix(api): validation casing for mixed tip use between single and eight channels

[CaseyBatten]

Overview

Closes RQA-2780
An edge case was found where the automatic tip tracking would not correctly identify the next valid column for an 8ch pickup after a sequence of single channel pickups.

Test Plan

The following protocol should pass analysis and perform identically on apiLevel 2.17 and 2.18.

requirements = {
	"robotType": "Flex",
	"apiLevel": "2.18"
}

def run(ctx):
	tips = ctx.load_labware('opentrons_flex_96_tiprack_1000ul', 'B3')
	tips2 = ctx.load_labware('opentrons_flex_96_tiprack_1000ul', 'C3')
	p1000 = ctx.load_instrument('flex_8channel_1000', 'right', tip_racks=[tips, tips2]) 
	p1000_single = ctx.load_instrument('flex_1channel_1000', 'left', tip_racks=[tips, tips2])
	trash = ctx.load_trash_bin("A3")

	p1000_single.pick_up_tip()
	p1000_single.drop_tip()
	p1000_single.pick_up_tip()
	p1000_single.drop_tip()

	for i in range(22):
		p1000.pick_up_tip()
		p1000.drop_tip()

Changelog

Review requests

Risk assessment

Low

[jbleon95]

Changes look good, should add a unit test to catch this but this is good for 7.3