feat: added new middleware to validate request query values

[javiermolinar]

What this PR does:
It adds a new middleware to centralize query validations. For now, it checks if a traceQL is valid. If not it returns a 400 error code.

For metrics_query_range and metrics_query the validation is done before the middleware is executed since it's required to compile the TraceQL query to create the combiner. In these two places, we can switch from a 500 error code to a 400 one.

Which issue(s) this PR fixes:
Fixes #3990

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[joe-elliott]

nice! let's add a simple e2e test to confirm we get a 400 back.

nit: rename query_validator_middleware.go to async_query_validator.go to match the other async pipeline items

[javiermolinar]

I clicked on close by mistake :P