Make cutoff for Foreign Audio Scan configurable

[woodstockathbf]

Describe the change or feature you'd like to see added to HandBrake:

The Foreign Audio Scan uses a fixed percentage (10%) as a cutoff value when searching for candidates. While this works for the vast majority of cases, occasionally edge cases arise, where FAS will exclude a candidate that has slightly more than that.

This can be seen in a review of the logs, if you know what to look for. The log information can be used to to manually choose to replace the FAS "track" in their request with the closest match.

Letting a user change the percentage in their preferences may allow them to move their "bar" to, say, 15% instead of 10%, and cover more cases for them.

Arguments against:

Truly an edge-case setting, rarely needed.
Yet Another Rarely Used, Fiddly Setting That Needs Precious UI Space.
(this request can be referenced later if someone else makes the same request)

What version of HandBrake are you currently using? (e.g., 1.0.0)

1.2.0

What operating system and version are you running? (e.g., Ubuntu 16.04 LTS, macOS 10.3 High Sierra, Windows 10 Creators Update)

Windows 7

HandBrake Activity Log (see https://handbrake.fr/docs/en/latest/help/activity-log.html)

Being an edge case, it is hard to come up with a log that shows the issue.

[bradleysepos]

Seems best implemented as an application preference.

[sr55]

Seems reasonable to me. Marking as an enhancement.