Update to 2.10.8

Changelog:
Overview of Changes from GIMP 2.10.6 to GIMP 2.10.8
===================================================

Core:

  - Use adaptive chunk size in GimpProjection when rendering the
    projection asynchronously, rather than using a fixed chunk size.
    This provides a better trade-off between throughput and
    responsiveness dynamically, based on how fast the processing is.

Tools:

  - In all selection tools, show error on attempt to
    subtract-from/intersect-with empty selection.
  - Fix text along path not working with vertical text.
  - Fix Text tool's frame position when undoing a move operation.
  - Streamline Text tool's drawing blocking/unblocking logic.
  - When moving a text layer using the text tool (through alt+drag),
    don't change the layer's box mode to "fixed", which is unnecessary,
    since the layer's size isn't affected.
  - Transform and deformation operations now maintain color for fully
    transparent pixels, making unerase and curves manipulation of alpha
    channel more reliable.
  - All transform tools now apply changes when you save or export/overwrite
    an image without pressing Enter first to confirm changes.
  - Heal, Dodge/Burn, Smudge, and Convolve tools now adjust the processed
    buffer and mask_buffer regions according to the changes made to the
    application region, as calculated by intersecting it with the
    drawable and mask extents. This fixes wrong application position
    when painting on a drawable whose origin is above/to the left of the
    image's origin, and there's a selection active.

Plug-ins:

  - Port all plug-ins to the new iterator API in GEGL.
  - Improve automatic detection of HEIC/HEIF files.
  - Improve RawTherapee discovery by looking up registry key (should
    become useful with RawTherapee 5.5 and more).

Usability:

  - Compatibility information in the Save dialog is now more understandable.
    The minimum GIMP version for the XCF file is always written down when it
    is GIMP 2.8 or over. The list of features warranting the minimum version
    is now listed in an expander container rather than as tooltip, which
    makes it more discoverable. The warning on compression is now displayed
    as its own text under the checkbox and not as additional text to the
    minimum GIMP version label.

CLI:

  - New self-explanatory --enable-win32-debug-console CLI option

Debugging:

  - New GimpBacktrace API provides an interface for creating and
    traversing multi-threaded backtraces, as well as querying symbol
    information. Backends are available for Linux and Windows.
  - Performance log recording now available in the Dashboard dock.
    The log contains a series of samples of the dashboard variables,
    as well as the full program backtrace, when available. As such,
    it essentially acts as a built-in profiler, which allows us to
    correlate program execution with the information available
    through the Dashboard.
  - New performance-log-expand.py tool decodes a delta-encoded
    performance log by expanding the deltas, producing a log where
    each sample (and other relevant elements) contain complete
    information. The structure of expanded logs is identical to that
    of delta-encoded logs, the expanded log simply has no deltas.
  - New performance-log-resolve.py tool resolves symbol information
    in backtraces. The logs produced by GIMP only specify the program
    counter at each stack frame, providing an address-map to map
    program-counter addresses to actual symbols separately. This tool
    looks up each program-counter address in the address map,
    incorporating the relevant symbol information directly into the
    backtrace.
  - New performance-log-deduce.py tool that statistically deduces the
    correct thread states based on backtrace address frequency, fixing
    local inaccuracies.
  - New performance-log-viewer.py tool that is a viewer for GIMP
    performance logs, with a sample-selection area at the top and an
    information area at the bottom. The sample-selection area visualizes
    the sampled variables and markers using a simultaneous set of plots,
    and displays the currently selected samples. The information area
    shows global information stored in the log, as well as information
    specific to the currently selected samples, including variable listing
    and statistics, full backtrace, and profile/call-graph information.

Translations:

  - Updated translations: Danish, Dutch, Finnish, German, Hungarian,
    Italian, Polish, Portuguese (Brazil), Spanish, Swedish, Ukrainian.


(ryoon)