fix: completion invoke in three different scenarios

[p-spacek]

What does this PR do?

fix: completion invoke in three different scenarios

1. with short nextLine - nested object
2. with a new line inside the object
3. on the first array item

---

1. when the cursor is closer to the next element than the previous one

example:
  sample:
    # cursore here
  a: test # 'a' is closer to the curseor then 'sample'

2. when the cursor is on the first line just inside the object

example:
  sample:
    # cursore here
    prop: test

3. when the cursor is on the first item array position

examples:
  # cursore here
  - sample:
       prop: test

What issues does this PR fix or reference?

no ref

Is it tested? How?

added unit tests

[coveralls]

Coverage increased (+0.1%) to 79.086% when pulling b32f6d8 on p-spacek:fix/completion-invoke-in-specail-cases into 2c86c8b on redhat-developer:main.