logsql: improve regex parsing error message

[hagen1778]

Is your feature request related to a problem? Please describe

Query field:~"(?i)\$" when executed returns the following error message:

cannot parse `query` arg: cannot read regexp for field "field": compound token cannot start with "\""; put it into quotes if needed; context: [field:~"]; query=field:~"(?i)\$"

The message is misleading, as it states that expression starts with ". It is likely because of \ char in the expression parser switches to the "raw" mode and treats " as denied compound token.

Describe the solution you'd like

Error message should be more meaningful for the user.

Describe alternatives you've considered

No response

Additional information

No response