GWC improvements:better resolution choice and Support HintsLevel

[dromagnoli]

Update resolution selection, now based on nearest match and support configuring HintsLevel on Layer definition.

[aaime]

Should check if hintsLevel is null and do something sensible, like maybe returning the default hints, to be consistent with TileLayer? Would also spare a few null checks in the codebase.

[aaime]

Since the hints levels have been added to the TileLayer, there is no need for this check I believe.

[dromagnoli]

All feedbacks have been addressed.

[geoserver-bot]

The backport to 1.28.x failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply 8b49b3d32... GWC improvements:better resolution choice and Support HintsLevel
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config set advice.mergeConflict false"

stdout

Auto-merging geowebcache/core/src/main/java/org/geowebcache/layer/TileLayer.java
Auto-merging geowebcache/core/src/main/java/org/geowebcache/layer/wms/WMSLayer.java
Auto-merging geowebcache/wms/src/main/java/org/geowebcache/service/wms/WMSService.java
Auto-merging geowebcache/wms/src/main/java/org/geowebcache/service/wms/WMSTileFuser.java
CONFLICT (content): Merge conflict in geowebcache/wms/src/main/java/org/geowebcache/service/wms/WMSTileFuser.java
Auto-merging geowebcache/wms/src/test/java/org/geowebcache/service/wms/WMSTileFuserTest.java

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.28.x 1.28.x
# Navigate to the new working tree
cd .worktrees/backport-1.28.x
# Create a new branch
git switch --create backport-1518-to-1.28.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 8b49b3d327df75ebcb657198024431eb3b8c5419
# Push it to GitHub
git push --set-upstream origin backport-1518-to-1.28.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.28.x

Then, create a pull request where the base branch is 1.28.x and the compare/head branch is backport-1518-to-1.28.x.