CLI: ansible-rulebook doesn't support non alphanumeric keys at the root level

We support non-alphanumeric keys in rules but only at the non root level
e.g.
event["a/b/c"] == "down" (root level a/b/c key) fails
event.data["a/b/c"] == "down" (data is the root level and a/b/c is the next level) works

The event is just a mnemonic that is stripped out before we send the AST to the Drools engine. The event doesn't exist in the payload coming from external sources
<what is happening>

The first error that we see is
2023-09-13 09:31:19,309 - ansible_rulebook.cli - ERROR - Terminating Invalid identifier : event["a/b/c"] Should start with event., events.,fact., facts. or vars.

Once this is fixed in ansible_rulebook by making it aware of the square bracket notation we get a Drools error
2023-09-12 16:48:52,847 - ansible_rulebook.cli - ERROR - Terminating java.lang.NullPointerException: Cannot invoke "org.antlr.v4.runtime.Token.getStopIndex()" because the return value of "org.antlr.v4.runtime.ParserRuleContext.getStop()" is null

Steps to Reproduce

Use the attached rulebook and run the ansible-rulebook

Actual Behavior

Failure in ansible-rulebook
Failure in drools

Expected Behavior

We should be able to support the dot notation or the square bracket notation at the root and non root levels when defining a condition