Fix swallowed I/O exceptions by replacing PrintWriter with (OutputStreamWriter/BufferedWriter)

[HarshMehta112]

Fixes : #1275

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PrintWriter suppresses IOException by design. Instead of propagating errors, it silently captures them and sets an internal error flag. As a result, any I/O failure during write operations can go unnoticed unless checkError() is explicitly invoked.

While the usage of PrintWriter in DefaultMessageHolder is safe (since it writes to an in-memory StringWriter, which cannot throw IOException), its usage in AbstractLineAggregatingHandler is problematic because that class performs actual I/O operations. This could cause write failures to be ignored, leading to incomplete or lost log output without any visibility into the underlying issue.

✅ Solution

Replaced PrintWriter with BufferedWriter in AbstractLineAggregatingHandler so that I/O errors are surfaced immediately via thrown exceptions.