feat: added split by line to DocumentSplitter

[srini047]

Related Issues

fixes #8519

Proposed Changes:

The new split_by value: line, has been introduced in the DocumentSplitter to enable users to split documents based on the \n character. This comes handy in multiple conditions like splitting CSV, etc.

[coveralls]

Pull Request Test Coverage Report for Build 11802880844

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 90.18%

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Files with Coverage Reduction	New Missed Lines	%
components/preprocessors/document_splitter.py	1	98.35%

Totals
Change from base Build 11660533312:	0.04%
Covered Lines:	7778
Relevant Lines:	8625

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💛 - Coveralls

[srini047]

@sjrl Can you review the PR.

[sjrl]

Left one comment, otherwise this looks good to me! But let's have @Amnah199 do the final review :)