IC2 shouldn't suggest reserved words as identifier names in completions, live templates, refactoring, etc.

Splintering this off from ~~#2598~~ as it’s a distinct issue from the original (and resolved one) documented there. Basically when IC2 suggests or auto-populates an identifier name, it should take care not to include reserved words in the offering that would result in Apex parser syntax errors. For example, instead of suggesting transaction, it should suggest txn.