Case Sensitive Move Operation

[rzvxa]

Description of Changes

Closes #1373 and potentially many unresolved issues on the subject of case insensitivity.
In this commit, I've introduced a new option called NERDTreeCaseInsensitiveFS which could also be used in the future to resolve similar issues in other places.
Until now the Move Operation used to check if the destination path already exists or not, On case-insensitive file systems this check fails if the user wants to move the file to a location with a different casing (for example moving/renaming foo.bar to FOO.BAR) as both paths point to the same file. With this new option, we can have an extra check to see whether or not the new destination is the same path in a different casing, and if that's the case we can ignore this false positive check.
With this new change came a wrong artifact, After the rename operation we check if an open buffer to this path exists or not.
Then we will point every window to that buffer to a new buffer for the new file path, vim doesn't acknowledge the new file path if it already has one open for the old casing file, I've used a temp buffer to compensate for this issue. Now we first redirect every window to a temp buffer, close the old buffer, and point windows looking at the temp buffer to this newly created one.
This part is written very clearly and has a lot of comments explaining each step of the process in the code itself.

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New Version Info

@alerque Sadly we skipped a few commits versioning, I would like to make a PR adding versions / CHANGELOG to the old merged PRs.
We can either block this PR until we fix the change log, or go ahead and merge it and give it a change log in the fix PR.

Author's Instructions

• Derive a new MAJOR.MINOR.PATCH version number. Increment the:
  • MAJOR version when you make incompatible API changes
  • MINOR version when you add functionality in a backwards-compatible manner
  • PATCH version when you make backwards-compatible bug fixes
• Update CHANGELOG.md, following the established pattern.

Collaborator's Instructions

• Review CHANGELOG.md, suggesting a different version number if necessary.
• After merging, tag the commit using these (Mac-compatible) bash commands:

  git checkout master
  git pull
  sed -n "$(grep -n -m2 '####' CHANGELOG.md | cut -f1 -d: | sed 'N;s/\n/,/')p" CHANGELOG.md | sed '$d'
  git tag -a $(read -p "Tag Name: " tag;echo $tag) -m"$(git show --quiet --pretty=%s)";git push origin --tags

[rzvxa]

I've gone through some iterations and tried to streamline our approach to potentially fix other similar issues using it.
I can confirm it works as intended on Windows, But it affects Mac users the most as there were some case-insensitive checks in place for Windows but not for macOS, and with this PR I've unified both operating systems under the new setting g:NERDTreeCaseSensitiveFS

[kevinkowalew]

I tested both 0 and 3 on macOS this morning and it achieves the desired behavior, should be good to merge 🎉

[alerque]

@kevinkowalew Thanks for testing and reporting, that's super helpful to move things forward!

[rzvxa]

Thanks to @kevinkowalew we have confirmation that these changes work on the macOS, I would've waited for @dangibson to give some feedback on this PR because he's also working on a similar issue in #1346 but since these changes are pretty essential and minor implementation details can always be changed in the subsequent patches I'm going to move forward with merging it into the upstream.