EXP-15601: Updated error log to include NSError for S7IniConfig

[kvoskovskiy]

Ticket link

EXP-15575

PR description

• What is the context for this PR?

Updated S7IniConfig.m + (instancetype)configWithContentsOfFile:(NSString *)filePath implementation to include NSError form initWithContentsOfFile error property or keep "Failed to read string content" error message if we read no content without any error.

• Why did you take the approach you did?

Screenshot / Videos

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PR submission checklist

• PR name contains Jira ticket number
• PR have correct target branch
• .s7substat has correct subrepos revisions
• Common (Obj-C / Swift) and your team's coding conventions and style guidelines are followed
• Unit tests to cover the critical parts of the code are written
• Relevant documentation updated / added if needed
• Self-reviewed using the self-review checklist prior to submitting a PR
• All recommendations from the How to create Pull Request document are followed

[pastey]

Thank you!