Simplifying discardOldestFileIfNeeded function

[hannah-smartbear]

Goal

The function had a fairly high overhead, making several copies of the list of files. The goal was to reduce this.

Changeset

• Return earlier if the number of files is less than the maxStoreCount (previously this wasn't checked until a second copy of the list had already been made)
• Sort the first file list by last modified timestamp, instead of copying into a list and then sorting

Testing

• Tests already written for this function are still applicable
• Tested this locally

[bugsnagbot]

Android notifier sizes

Format	Size impact of Bugsnag (kB)	Size impact of Bugsnag when Minified (kB)
APK	1854.01	1674.7
arm64_v8a	631.04	450.82
armeabi_v7a	565.51	385.29
x86	708.85	528.62
x86_64	676.09	495.86

Generated by 🚫 Danger

[lemnik]

LGTM