Overview: fix sum-detail display, add entry method coloring and time axis labels

[lvkale]

Follow-on to #159, in the same lightly-exercised summary-detail paths, this time in the Overview (Small Time Line) tool. What sent me looking was a flood of NullPointerExceptions from picking entry colors; the display underneath turned out to be wrong in three further ways.

Overview on summary-detail traces

• Utilization was indexed by absolute PE number. The panel indexes its rows by position in the selected PE list, but the data came from getSumDetailData_PE_interval(), which is allocated over every PE in the run. Any PE subset drew the wrong rows, and rows for unselected PEs were zeros. It now uses getSystemUsageData(), which is already indexed by selected PE, relative to the loaded range, and converted to percent.
• Idle was indexed by absolute PE and absolute .sum interval but read with a range-relative index, so any range not starting at interval 0 reported idle from the wrong point in time. Idle is now rebuilt per selected PE, mapping .sumd intervals to .sum intervals by time since the two files can be binned differently, and capped at what the entry methods leave free — the same reconciliation Sum-detail traces: reconcile .sum idle with .sumd entry times, and speed up bar drawing #159 gave Time Profile and Usage Profile.
• The percent conversion stopped one interval short, leaving the last interval as raw microseconds (~1000 on a 1 ms bin) fed to a 0-255 color map. That is the source of the Warning: Invalid value ... being applied to the color map lines.
• "Color By: Entry Method" was never offered, though .sumd files carry per-entry-method data. IntervalData now records the dominant entry method per (PE, interval) while it expands the RLE data, and the mode is available. Intervals with no recorded entry method time, or that the .sum file says were mostly idle, draw as idle.
• The NPE: the "Choose Entry Method Colors" button was created unconditionally while the radio button colorsHaveChanged() calls isSelected() on was created only for .log traces.

Color chooser

The chooser now gets an EntryMethodVisibility filter from Overview, so it lists only the entry methods actually drawn instead of every one in the run (411 on my trace), reusing the mechanism #157 added for Time Profile. Idle and Overhead are left out, because Overview draws them white and black regardless of the palette — picking colors for them did nothing. Note this also removes those two rows for .log traces, where they were previously listed but equally inert.

It also gained a Done button. The window had no obvious way to be dismissed; colors still take effect as they are picked. This is in the shared ChooseEntriesWindow, so Timeline, Histogram, Time Profile and Usage Profile get it too — those keep their Idle/Overhead rows, which is correct since they really do draw those colors. And ChooseEntriesWindow now asks for the entry list once instead of on every row, because some tools answer that question by scanning their whole display.

Time axis labels

Overview's bottom ruler already drew tick marks that tracked pan and zoom, and getTicks() already returned each tick's value — nothing drew it as text. ScalePanel gained an AxisLabeler hook and now writes timestamps under the ticks, placed longest-tick-first with collision avoidance so the roundest numbers get the room and zooming in reveals more labels. ScalePanel is used only by this tool.

Testing

Manually verified by @lvkale on a 4-PE and a 1920-PE summary-detail trace (full range, PE subsets, sub-ranges, both color modes, axis labels) and a 120-PE .log trace, which ran clean; the Done button was checked in Timeline, Histogram, Time Profile and Usage Profile. Each commit builds on its own. make test passes.

Known limitation, filed separately as #160: Overview's per-PE-per-interval arrays are ~1.5 GB on the 1920-PE trace inside the launcher's 5 GB heap, so this will not scale far past that PE count. The issue lists three reclaims worth ~950 MB with no behavior change.