[Masking] Fix copy/paste of symbol or converting renderer

[troopa81]

Properly reset symbol layer ids when copy/pasting symbol or when converting a rule based renderer into a categorized renderer.

Fixes #46402 where issues comes from symbol layers having identical symbol layers ids, coming from I presume, actions described just above

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit dc2e6b3)

🪟 Windows Qt6 builds

Download Windows Qt6 builds of this PR for testing.
(Built from commit dc2e6b3)

[qgis-bot]

The backport to release-3_40 failed:

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

stderr

error: could not apply 2bd0d2eaaf1... fix(SymbolCopyPaste): reset symbol layer ids on copy/paste
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 python/PyQt6/core/auto_generated/symbology/qgssymbollayer.sip.in
Auto-merging python/core/auto_generated/symbology/qgssymbollayer.sip.in
Auto-merging src/core/symbology/qgssymbollayer.cpp
Auto-merging src/core/symbology/qgssymbollayer.h
Auto-merging src/core/symbology/qgssymbollayerutils.cpp
Auto-merging tests/src/python/test_qgscategorizedsymbolrenderer.py
[backport-60325-to-release-3_40 413b52b641f] fix(CategorizedRenderer): reset mask information on source symbol
 Author: Julien Cabieces <julien.cabieces@oslandia.com>
 Date: Tue Jan 28 15:32:49 2025 +0100
 16 files changed, 123 insertions(+), 7 deletions(-)
[backport-60325-to-release-3_40 5d699df9207] clean(MaskingWidget): remove unused variables
 Author: Julien Cabieces <julien.cabieces@oslandia.com>
 Date: Tue Jan 28 15:38:39 2025 +0100
 2 files changed, 4 insertions(+), 10 deletions(-)
Auto-merging src/app/qgsapplayertreeviewmenuprovider.cpp
CONFLICT (content): Merge conflict in src/app/qgsapplayertreeviewmenuprovider.cpp

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-release-3_40 release-3_40
# Navigate to the new working tree
cd .worktrees/backport-release-3_40
# Create a new branch
git switch --create backport-60325-to-release-3_40
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick c26cf427006070f4c11d7712b017efe0a15dac70,24aeb7ea95a6f547d40f1c485d850951c6ab93ed,2bd0d2eaaf1329ac5ba4e611bc67d306d085c0d8,dc2e6b3f79185459ec3f531a7a8021df328c972d
# Push it to GitHub
git push --set-upstream origin backport-60325-to-release-3_40
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-3_40

Then, create a pull request where the base branch is release-3_40 and the compare/head branch is backport-60325-to-release-3_40.

[agiudiceandrea]

Please see #46402 (comment).