rework *enabled* accounting for CLJS compiletime/runtime

[dustingetz]

• Perhaps two flags – *erase* and *enable* (or *disable*)
• Should we make everything run by default?

List of cases when we do NOT want tests to run:

• do not test on JVM REPL startup (big projects do not want to load any namespaces at all for fast REPL startup times)
• do not test during clojurescript hot code reload (JS runtime)
• do not test during clojurescript macroexpansion (JVM macroexpansion time), see Disable RCF in the JVM during CLJS build (in :require-macros scenario) #67
• tests should erase entirely in prod

There may be some other way to design the flags to achieve these behaviors. The requirement to erase tests by default perhaps can be waived if other reqs are met.

[dustingetz]

https://clojurians.slack.com/archives/C7Q9GSHFV/p1661662217708859