Refactor list and map mutations

[kekavc24]

This PR improves #90 by:

1. Refactoring skipAndExtractComments:
   • Fixes an issue where the function never exits if more than one comment is encountered. My bad!
   • Prevents the function from eagerly skipping line-breaks within the loop. This was causing in faulty edits.
2. Introduces a reclaimIndentAndLineBreak function for taking back indent greedily consumed by skipAndExtractComments when removing an element or entry within a YamlList or YamlMap respectively.
3. Refactors functions that mutate block lists and maps to take advantage of skipAndExtractComments and reclaimIndentAndLineBreak which include:
   • _appendToBlockList and _removeFromBlockList in lists.
   • _removeFromBlockMap in maps.

Completely aligns the changes from #90 and #93 with existing YamlEditor behaviour.

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[kekavc24]

@jonasfj it could be argued that the code that finally does the adjustment of the startOffset
and endOffset is quite similar for both _removeFromBlockList and _removeFromBlockMap once I deal with the nuances yaml has for each:

For list mutations:
https://github.com/kekavc24/yaml_edit/blob/7378e9212575ddcea4627fef0cb28ab7d6b53fec/lib/src/list_mutations.dart#L343-L426

For map mutations:
https://github.com/kekavc24/yaml_edit/blob/7378e9212575ddcea4627fef0cb28ab7d6b53fec/lib/src/map_mutations.dart#L214-L285

Is it "DRY"-worthy? I thought of extracting it to a function.