* Renamed 1 of 2 SyncScrollOffset props, for clarity
The property "SyncScrollOffset" in TextDiff is distinct from the one with the same name in TwoSideTextDiff. These two properties are used in separate (though slightly related) ways and are not really connected.
The one in TwoSideTextDiff is mainly used to keep the scroll-pos of the two SingleSideTextDiffPresenter views in sync (aligned), while the one in TextDiff is used only to preserve/reset the scroll-pos in the single CombinedTextDiffPresenter view when (re)loading Diff Content (so not really syncing anything).
To clarify this and to make the two properties more distinguishable, I renamed the one in TextDiff to simply "ScrollOffset".
* Added icon and string for "Show All Lines"
New StreamGeometry "Icons.Lines.All" using SVG path from "text_line_spacing_regular" at https://avaloniaui.github.io/icons.html.
New String "Text.Diff.VisualLines.All" for en_US locale (no translations yet).
* Implemented new TextDiff feature "Show All Lines" (toggle)
* Added new ToggleButton in DiffView toolbar, visible when IsTextDiff, disabling the buttons "Increase/Decrease Number of Visible Lines" when on.
* Added new Preference property "UseFullTextDiff".
* Added StyledProperty "UseFullTextDiffProperty" in TextDiffView, with a DataTemplate binding to the corresponding preference property.
* When changed, UseFullTextDiffProperty is handled identically as UseSideBySideDiffProperty (via new helper method RefreshContent(), for unification with OnDataContextChanged()).
* Added new method DiffContext.ToggleFullTextDiff() for changing the preference property and reloading the diff content.
* Implemented the new feature by overriding the "unified" (number of context lines) for Commands.Diff() with a very high number.
NOTE: The number used (~1 billion) is supposed to be the highest one working on Mac, according to this forum comment: https://stackoverflow.com/questions/28727424/for-git-diff-is-there-a-uinfinity-option-to-show-the-whole-file#comment135202820_28846576
* replace icon with common whitespace icon in other editors
* button tooltip translations
* rename `_showHiddenSymbols` to `_showHiddenSymbolsInDiffView` to make its usage clear
* change the order of this button
* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.
