reduce guava code usage

[sebthom]

This PR addresses #865 and removes most usages of the guava library.

The only location left is at

lsp4e/org.eclipse.lsp4e/src/org/eclipse/lsp4e/outline/SymbolsLabelProvider.java

Lines 185 to 227 in 680b765

	protected int getMaxSeverity(@NonNull IResource resource, @NonNull IDocument doc, @NonNull Range range)
	throws CoreException, BadLocationException {
	if (!severities.containsKey(resource)) {
	refreshMarkersByLine(resource);
	}
	RangeMap<Integer, Integer> severitiesForResource = severities.get(resource);
	if (severitiesForResource == null) {
	return -1;
	}
	int bound1 = LSPEclipseUtils.toOffset(range.getStart(), doc);
	int bound2 = LSPEclipseUtils.toOffset(range.getEnd(), doc);
	// using bounds here because doc may have changed in the meantime so toOffset can return wrong results.
	com.google.common.collect.Range<Integer> subRange = com.google.common.collect.Range.closed(
	Math.min(bound1, bound2), // we guard that lower <= endOffset
	bound2);
	return severitiesForResource.subRangeMap(subRange)
	.asMapOfRanges()
	.values()
	.stream()
	.max(Comparator.naturalOrder())
	.orElse(-1);
	}
	private void refreshMarkersByLine(IResource resource) throws CoreException {
	RangeMap<Integer, Integer> rangeMap = TreeRangeMap.create();
	Arrays.stream(resource.findMarkers(IMarker.PROBLEM, true, IResource.DEPTH_ZERO))
	.filter(marker -> marker.getAttribute(IMarker.SEVERITY, -1) > IMarker.SEVERITY_INFO)
	.sorted(Comparator.comparingInt(marker -> marker.getAttribute(IMarker.SEVERITY, -1)))
	.forEach(marker -> {
	int start = marker.getAttribute(IMarker.CHAR_START, -1);
	int end = marker.getAttribute(IMarker.CHAR_END, -1);
	if (end < start) {
	end = start;
	}
	int severity = marker.getAttribute(IMarker.SEVERITY, -1);
	if (start != end) {
	com.google.common.collect.Range<Integer> markerRange = com.google.common.collect.Range.closed(start,end - 1);
	rangeMap.remove(markerRange);
	rangeMap.put(markerRange, severity);
	}
	});
	severities.put(resource, rangeMap);
	}

where com.google.common.collect.RangeMap is used.

I cannot really wrap my head around that code introduced by @mickaelistria with ae5a762. Maybe he is able to change the implementation to not require guava.

[mickaelistria]

The change here doesn't make things simpler. So I wouldn't merge it yet if it's not enabling us to fully remove guava.
The getMaxServerity is a way to get the highest severity that affects a range: LSP diagnostics are attached to ranges, some can be overlapping, and the RangeMap allows to easily access the diagnostics for a range, including the included or overlapping ranges. I'm not aware of a better structure for that in standard JDK.

[mickaelistria]

The initial target branch master was deleted and replaced by main, so this PR got closed automatically. If this is still relevant, please re-create this PR targetting the main branch.