Add a new known issue for replacement phase 1 rules

If completely replacing a CRS phase 1 rule (not just updating a rule target etc. but completely replacing a rule, i.e. the operator is being modified) then this cannot occur in the REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf file because any anomaly scoring will be wiped and set to 0 immediately after when REQUEST-901-INITIALIZATION.conf executes.

RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf is also no good as the replacement rule needs to come before REQUEST-949-BLOCKING-EVALUATION.conf/RESPONSE-959-BLOCKING-EVALUATION.conf so that the replacement rule correctly contributes to anomaly scoring totals. Otherwise, things like early blocking mode can start to break.

Document corner case as a known issue.

Include two ideas as solutions:

• SecRuleRemoveById and then add new rule, all after the includes
• Add in a custom REQUEST-902-CUSTOM-RULES-POST-INIT file, or something similar, if there are going to be many such replacement rules

Reference: https://github.com/coreruleset/coreruleset/pull/2878