fix panics when cloning a special query

[garrettlish]

What this PR does / why we need it:
Sometimes we will get panics when parse the expression which is cloning a special query: syntax error: unexpected $end, expecting NUMBER or { or (", line:1, col:1025}.

Which issue(s) this PR fixes:
Fixes #7155

Special notes for your reviewer:
N/A

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• CHANGELOG.md updated
• Changes that require user attention or interaction to upgrade are documented in docs/sources/upgrading/_index.md

[dannykopping]

@garrettlish can you please explain why this change should fix the issue?
This breaks other tests btw: https://drone.grafana.net/grafana/loki/20419/3/5

I would appreciate if you could reduce those test cases down to more simple forms, which describe the actual problem at hand; these queries are complex and they will be difficult to interpret by future readers.

[garrettlish]

@dannykopping sorry for break other tests in the first commit. I add that complex query is because the syntax parse will panic for these kinds of complex queries only, looks like goyacc cannot parse the complex queries properly if we don't have space between by and (, let me try to refine the query.

[dannykopping]

Thanks!

The fix looks good, but I think we should address the underlying panic as well.
I'll raise this with the team 👍

[grafanabot]

Hello @DylanGuedes!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!