Bug 2008722 - Directly use the pixel-based size for the SplitPane resize.

[arai-a]

for https://bugzilla.mozilla.org/show_bug.cgi?id=2008722

This does:

• Store the pixel-based height of the resize event into the job-view App state
• Directly use the pixel-based height for the details panel if the window height haven't changed since the last resize
• Calculate the height of the details panel based on the ratio when the window height has changed since the last resize
• Simplify the default size calculation