Use block scalars in YAML dumps

[sgsunder]

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What does this PR do and why is it necessary?

This is a minor tweak that improves the look of multiline string values that are dumped as YAML. Most often, it makes GCODE scripts stored inline in the config.yaml file look much easier to read and to hand parse.

Before:

  bedlevelvisualizer:
    _config_version: 1
    command: M420 T0 V
    commands:
    - command: 'M190 R%(bedtemp)s

        G34

        G29'
      confirmation: true
      enabled_while_graphing: false
      enabled_while_printing: false

After:

  bedlevelvisualizer:
    _config_version: 1
    command: M420 T0 V
    commands:
    - command: |-
        M190 R%(bedtemp)s
        G34
        G29
      confirmation: true
      enabled_while_graphing: false
      enabled_while_printing: false

Both statements parse equivalently so it should not have any effect on functionality. This change is only intended to make it easier for humans to read and modify.

How was it tested? How can it be tested by the reviewer?

• Ran pytest (Passed with no errors).
• Ran against a copy of my personal config.yaml file. (No errors found).

Any background context you want to provide?

N/A

What are the relevant tickets if any?

No open issues could be found regarding this.

Screenshots (if appropriate)

N/A

Further notes

[foosel]

Thank you, that's a lovely QOL change!