Remove tibble warnings in `render_graph()`

[olivroy]

Basically, I refactored the code by:

1. return early if output is vistnetwork. (hence the large diff, no longer to nest the code in a if condition)
2. Use vectors to access the matrix columns instead of using as_tibble()
3. We error earlier if the layout is not in one of the allowed values
4. I take some of the common code for each layout and avoid code duplication, only applying correction for the "circle" layout.
5. Added tests to verify no warning were produced.

I was also able to simplify a condition

# before 
 y * (((count_nodes(graph) + (0.25 * count_nodes(graph)))) / count_nodes(graph)))
# from what I can tell
# this can be simplified to
y * 1.25
# please double check if I am correct.

I suggest looking at the diff side by side since it doesn't look too good inline.

Rationale

The example in README

library(DiagrammeR)
example_graph <-
  create_graph() %>%
  add_pa_graph(
    n = 50, m = 1,
    set_seed = 23
  ) %>%
  add_gnp_graph(
    n = 50, p = 1/100,
    set_seed = 23
  ) %>%
  join_node_attrs(df = get_betweenness(.)) %>%
  join_node_attrs(df = get_degree_total(.)) %>%
  colorize_node_attrs(
    node_attr_from = total_degree,
    node_attr_to = fillcolor,
    palette = "Greens",
    alpha = 90
  ) %>%
  rescale_node_attrs(
    node_attr_from = betweenness,
    to_lower_bound = 0.5,
    to_upper_bound = 1.0,
    node_attr_to = height
  ) %>%
  select_nodes_by_id(nodes = get_articulation_points(.)) %>%
  set_node_attrs_ws(node_attr = peripheries, value = 2) %>%
  set_node_attrs_ws(node_attr = penwidth, value = 3) %>%
  clear_selection() %>%
  set_node_attr_to_display(attr = NULL)

render_graph(example_graph, layout = "nicely")

Warning message:
The `x` argument of `as_tibble.matrix()` must have unique column names if
`.name_repair` is omitted as of tibble 2.0.0.
ℹ Using compatibility `.name_repair`.
ℹ The deprecated feature was likely used in the DiagrammeR package.
  Please report the issue at <https://github.com/rich-iannone/DiagrammeR/issues>.
This warning is displayed once every 8 hours.
Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
generated. 

[olivroy]

@rich-iannone I scanned through the issues quickly, would you mind closing #474, #483, #438, #417, #389, #334, #297, #277 (#477, #501, #480, #473, #470, #421, #363 as duplicate of #475 (keep #475 open, maybe pin it?)

[rich-iannone]

This I can do! I'll start on it now.

[olivroy]

Thanks also #278, #366

[rich-iannone]

Not sure why I didn't do this sooner but I'm adding you as a collaborator on the repo. That should definitely help with issue management and other repo actions!

[olivroy]

Fyi, I do not plan to merge the PRs (unless you approve them), I just wanted to see if they passed R CMD CHECK