Fix last split cannot be resized

[masmu]

vResizeSplit and hResizeSplit cannot change the size of the last split in a group of siblings. It resizes the split before the last split instead.

How to reproduce:

PLUGIN_VERSION = "2.0.0"
PLUGIN_NAME = "bug_last_split_cannot_be_resized"

local micro = import("micro")
local buffer = import("micro/buffer")

function resizePane(bp, id, size)
    local tab = bp:Tab()
    local paneIndex = tab:GetPane(id)
    local pane = tab.Panes[paneIndex + 1]
    pane:ResizePane(size)
    tab:SetActive(paneIndex)
end

function createSplits(bp, num)
    local tab = bp:Tab()
    local currentBp = bp
    while true do
        currentBp.Buf:Insert(
            buffer.Loc(1, 1), string.format("pane%s", currentBp:ID()))
        if #tab.Panes >= num then break end
        local newBuf, err = buffer.NewBufferFromFile("")
        currentBp = currentBp:VSplitIndex(newBuf, true)
    end
    tab:SetActive(bp:ID() - 1)
end

function postinit()
    local bp = micro.CurPane()
    if bp.Buf:Size() > 0 then
        return
    end

    createSplits(bp, 3)

    -- resizePane(bp, 1, 30)  -- this works
    -- resizePane(bp, 2, 30)  -- this works

    -- this does not work and sets the size of pane 2 instead
    resizePane(bp, 3, 30)
end

At first, I just fixed the bug, but then I found the entire design of vResizeSplit and hResizeSplit a bit strange.
So I thought it would be a good idea to change vResizeSplit and hResizeSplit so that they work the same way as VSplit and HSplit. This way, you can easily select the direction in which you want to resize. With the old design, you have to use a lot of extra logic in Lua to enable resizing to the left or top.

Fixes #3046

[masmu]

I forgot to mention this fixes issues/3046.

[Neko-Box-Coder]

Yeah got the same issure when resizing and worked around it by just resizing the previous one 😂

https://github.com/Neko-Box-Coder/MicroOmni/blob/db958a6ba831b962b3619e5d3a8e961d92f5280f/MicroOmni.lua#L108-L113

    -- NOTE: Dumb hack where ResizePane() actually resizes the previous node if the current node 
    --       is at the end
    if isEnd then
        n = n * -1
        node = prevNode
    end

It's good to fix this but the change of function signature will break any plugins that use it, is there a way around it? At least for bufpane?