Expose Settings for Build Report Inspector to allow custom date formatting

[KesKim]

BuildReportInspector hard-codes build report output path but more importantly it hard-codes the filename date formatting in a way I find unacceptable: using Unity Build Reporter as a Package Manager package my only option currently is manually renaming every file after Build Report Inspector creates it.

This is the hard-coding in question

var assetPath = buildReportDir + "/Build_" + date.ToString("yyyy-dd-MMM-HH-mm-ss") + ".buildreport";

Resulting in a filename like "Build-2020-15-kesä-15-59-06" on my computer, which is neither what I prefer but more importantly does not sort chronologically for quick and legible browsing and organizing (Project Assets view is sorted alphabetically and hard-coded format does not sort the entries in any chronological order which is relevant when making comparisons of the builds as chronological series).

I'd much prefer if you expose a Settings UI for customizing the defalt filename date formatting when outputting .buildreport files, but failing that you could just hardcode it in ISO 8601 "YYYY-MM-DD-hh-mm-ss" as described in https://en.wikipedia.org/wiki/ISO_8601