fix: retrieve cookie name at runtime

[mcollovati]

Quarkus 3.19 refactors HTTP configuration in a way that cookie name is available only at runtime.
This change move the configuration retrival inside the Supplier returned by setupFormAuthenticationMechanism so that the configuration can be retrieved.

Fixes #1270

[quarkus-hilla-bot]

Format Checker Report

All files are correctly formatted

[github-actions]

Test Results

102 files  +29  102 suites  +29   18m 12s ⏱️ + 7m 43s
298 tests +44  286 ✅ +44  12 💤 ±0  0 ❌ ±0 
456 runs  +98  438 ✅ +98  18 💤 ±0  0 ❌ ±0 

Results for commit 066266d. ± Comparison against base commit afde71c.

[mcollovati]

The change fixed the Quarkus ecosystem CI build https://github.com/mcollovati/quarkus-hilla/actions/runs/13203981863

[github-actions]

This issue has been resolved in 24.7.0-alpha2 (Release
Notes)

[quarkus-hilla-bot]

The backport to 24.6 failed:

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

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-24.6 24.6
# Navigate to the new working tree
cd .worktrees/backport-24.6
# Create a new branch
git switch --create cherry/cherrypick-1276-to-24.6
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 95e1ba04edf0e8f931fa58ac8bc4c5a3494d70d9
# Push it to GitHub
git push --set-upstream origin cherry/cherrypick-1276-to-24.6
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-24.6

Then, create a pull request where the base branch is 24.6 and the compare/head branch is cherry/cherrypick-1276-to-24.6.