Update doc dql-custom-walkers.rst with an output walker to interpolate parameters into SQL

[n0099]

#11959

[greg0ire]

Sorry for inadvertently closing your other PR yesterday, it was because I deleted the target branch.

Please kindly squash your commits together. If you don't, we'll try to remember to do it for you but it's best if you save us this trouble.

How to do that?

1. git rebase -i origin/3.5.x, assuming origin is a git remote that points to this repository, and not your fork. If you're not sure what your remotes are, run git remote -vvv, there should be your fork and the holy/reference/base/origin/whatever-you-call-it repository.
2. A window will show up with many lines, replace pick with fixup on every line but the first one
3. Close your editor, git should do its magic, and you should end up with one commit
4. Use git push --force to overwrite what you already pushed. Don't forget the --force option otherwise git will try to merge both things together.

[github-actions]

There hasn't been any activity on this pull request in the past 90 days, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 7 days.
If you want to continue working on it, please leave a comment.

[n0099]

bump

[greg0ire]

You should elaborate here. I think your need is to get a SQL statement that you can replay yourself, with an SQL client. If so, please say so explicitly and clearly.

[n0099]

For me there's two main usage of raw SQL: log the SQL being executed to debug possible slow queries in future, and UNION results of multiple DQL with WHERE as only DBAL query supports UNION as in https://stackoverflow.com/questions/4155288/how-to-write-union-in-doctrine-2-0/79647475#79647475 and https://github.com/n0099/open-tbm/blob/c960f09242097937403880a6ebd02ef4946ce3a8/be/src/PostsQuery/QueryResult.php#L219-L237.

[n0099]

Suggested change

	Sometimes we may want to log or trace the raw SQL being generated from its DQL,
	Sometimes we may want to log or trace the raw SQL being generated from its DQL
	for profiling slow queries in the future or audit queries that changed many rows