RFR: 8349083: Factor out filename handling code from logging

[David Holmes]

On Sat, 1 Feb 2025 16:53:13 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Factor out filename substitution code from unified logging, so that it can be used elsewhere:
> 
> 1. Make filename substitution consistent.  Support following substitutions cross JVM
> ```   
>    %p -> pid
>    %t -> timestamp
>    %hn -> hostname
> 
> 
> 2. Reduce redundant code

The hope was we would have a range of time specifiers for different notion of timestamp - but given different uses of %t already exist that would be problematic.

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PR Comment: https://git.openjdk.org/jdk/pull/23410#issuecomment-2655543708