fix: normalize HTTPRoute header and query matches

[tao12345666333]

What this PR does / why we need it:

According to the semantics of the Gateway API, header names should be case insensitive.

https://gateway-api.sigs.k8s.io/reference/api-spec/1.5/spec/#httpheadermatch

Name is the name of the HTTP Header to be matched. Name matching MUST be
case-insensitive. (See https://tools.ietf.org/html/rfc7230#section-3.2).
If multiple entries specify equivalent header names, only the first
entry with an equivalent name MUST be considered for a match. Subsequent
entries with an equivalent header name MUST be ignored. Due to the
case-insensitivity of header names, “foo” and “Foo” are considered
equivalent.

Which issue this PR fixes

Fixes #4598

Special notes for your reviewer:

I actually discovered this issue while handling #4563. I think it is relatively independent and can be addressed as a separate PR.

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect significant changes

[programmer04]

Maybe it would be worth mentioning this in the changelog, wdyt?

[tao12345666333]

@programmer04 Thank you! Added a82c7bb

[team-k8s-bot]

The backport to release/2.2.x 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-release/2.2.x release/2.2.x
# Navigate to the new working tree
cd .worktrees/backport-release/2.2.x
# Create a new branch
git switch --create backport-4597-to-release/2.2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 dbfdcaac315c4b5949cc50b5cb2aa69b3caa38f4
# Push it to GitHub
git push --set-upstream origin backport-4597-to-release/2.2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release/2.2.x

Then, create a pull request where the base branch is release/2.2.x and the compare/head branch is backport-4597-to-release/2.2.x.