Rename Zest index.html to guide.html

So that it's consistent with the Draw2D and GEF naming convention.

Undeprecate public methods in ScaledGraphics eclipse-gef#1030

The deprecated `ScaledGraphics` class is extended by the `PrintGraphics`
class. If a method defined by the `Graphics` class hasn't been
overridden in the `PrinterGraphics`, this deprecation warning is
propagated, even though the `PrinterGraphics` is not deprecated.

Closes eclipse-gef#1030

Only use double-precision translation when HighDPI scaling is enabled

When the "draw2d.enableAutoscale" system property is enabled, additional
(scalable) layers are injected into the IFigure hierarchy to take the
monitor zoom into consideration.

As a result of this, translating geometric shapes may cause additional
rounding errors, which are the result of translating integer-values with
an additional, fractional zoom level.

To work around this problem, the "useDoublePrecision()" method was added
with 5cfe5b7, which converts the
geometric shapes to their precise variants. This conversion is generally
not backwards compatible.

To make sure clients can fully opt-out of this new behavior, this
conversion should only be done when the "draw2d.enableAutoscale" is set
to true, meaning only when these new layers are added, that require this
extended translation logic.

Make disposal of BufferedGraphicsSource more robust eclipse-gef#875

The call to GC.drawImage() may throw an IllegalArgumentException when
dealing with fractional scaling. In such a case, not all SWT resources
are destroyed, leading to memory leaks.

Any exception thrown by this operation is caught and logged, in order to
allow the disposal to finish gracefully.

Closes eclipse-gef#875

Bump actions/setup-java from 4.7.1 to 5.0.0

Bumps [actions/setup-java](https://github.com/actions/setup-java) from 4.7.1 to 5.0.0.
- [Release notes](https://github.com/actions/setup-java/releases)
- [Commits](actions/setup-java@c5195ef...dded088)

---
updated-dependencies:
- dependency-name: actions/setup-java
  dependency-version: 5.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Revert "Cleanup GEF cursors and remove some of the blockiness"

This reverts commit 537b65f.

Bump actions/upload-artifact from 4.6.0 to 4.6.1

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4.6.0 to 4.6.1.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@65c4c4a...4cec3d8)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Publish build results from Jenkins to GitHub

This initial step is just about how to get the results (e.g. compiler
warnings) to GitHub. In a later stage, those can the be further
configured to have the build fail if it would introduce additional
warnings.

Update changelog for 3.21 release

Integrate Zest-based examples into our test suite

With this change, we instantiate and verify the correctness of the Zest
examples as part of our JUnit test suite. Special care needs to be
taken, in order to make sure that the examples can be used in the test
environment, but also still be executed as standalone applications.

This means that those snippets must not create a new Display instance,
as one is already created by the test suite and multiple displays are
forbidden. The snippet is then instantiated by reflectively calling the
main method.

Because the snippets block until the shell is closed by the user, a
little trick is needed to allow for the tests to be executed. The actual
test is scheduled as an asynchronous task before the snippet is created,
which is then executed by the call to "Display.readAndDispatch()".

For this exact reason has the FileDialog been removed from
GraphJFaceSnippet3, as this would block the UI thread prematurely, thus
making testing impossible. The example is still functional, as it will
instead load the example file from the classpath.

In almost all cases, the SpringLayoutAlgorithm of the code snippets has
been replaced by a GridLayout, in order to make the test more stable and
reproducible.

This contribution is done in preparation for the Zest 2.0 migration as a
means to increase the test coverage and thus spot any changes that are
introduced.