Fix symlinks being generated on Linux

[HebaruSan]

Problem

#4441 intended to suppress symlinks when cloning instances on Linux, but it didn't work; symlinks are still being generated.

Reported by @PewPewCricket on Discord and #4441 (comment).

Cause

I updated the default for the Checked property, but CheckedState is set to the opposite value on the next line, so the hidden checkbox was still always checked. 🤦

Changes

• Now CheckedState defaults to Unchecked, so there will actually not be symlinks on Linux.
• ini-parser's actual latest version is 2.5.2; 3.4.0 was a typo'd duplicate of 2.4.0 that was de-listed from Nuget. However, Nuget does not allow fully deleting releases, because it would break builds.
  Our reference is now updated from 3.4.0 to 2.5.2.

[coveralls]

Pull Request Test Coverage Report for Build 22550387682

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.09%) to 85.278%

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Files with Coverage Reduction	New Missed Lines	%
Core/Net/NetFileCache.cs	3	90.33%

Totals
Change from base Build 22150926659:	0.09%
Covered Lines:	11947
Relevant Lines:	14189

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💛 - Coveralls

[hpax]

I recently ran into this issue and looked at it in some detail. If it is desirable to create symlinks for the purpose of saving storage, it does work correctly if the symlink tree is created one level further down, i.e. instead of linking KSP_Data linking the contents of KSP_Data. I "repaired" the instances on my system by using the attached shell script which did exactly this.
kspfix.sh

That being said, this is not an issue if the data is on the same file system and hard links are used instead.

(I did not mess with KSPLauncher_Data since it didn't seem to have the same problem as KSP_Data.)