perf(router): unify cache key and context generation in expressions r…

…outer (#12127)

Cache key and context generation are closely related on field present inside configured expressions.

It is advantageous to unify the logic for generating them to:

1. Improve cache hit rate, so that only fields referenced inside expressions participates in cache
key generation. This is particularly important since we plan on adding more match fields into
expressions in the future
2. Improve performance, allows field value to be cached and reused between cache key and context generation
3. Reduced code duplication

KAG-3032

kong-3.4.3-0.rockspec

@@ -50,12 +50,6 @@ build = {
     ["kong.cache"] = "kong/cache/init.lua",
     ["kong.cache.warmup"] = "kong/cache/warmup.lua",
     ["kong.global"] = "kong/global.lua",
-    ["kong.router"] = "kong/router/init.lua",
-    ["kong.router.traditional"] = "kong/router/traditional.lua",
-    ["kong.router.compat"] = "kong/router/compat.lua",
-    ["kong.router.expressions"] = "kong/router/expressions.lua",
-    ["kong.router.atc"] = "kong/router/atc.lua",
-    ["kong.router.utils"] = "kong/router/utils.lua",
     ["kong.reports"] = "kong/reports.lua",
     ["kong.constants"] = "kong/constants.lua",
     ["kong.concurrency"] = "kong/concurrency.lua",
@@ -64,6 +58,14 @@ build = {
     ["kong.error_handlers"] = "kong/error_handlers.lua",
     ["kong.hooks"] = "kong/hooks.lua",
 
+    ["kong.router"] = "kong/router/init.lua",
+    ["kong.router.traditional"] = "kong/router/traditional.lua",
+    ["kong.router.compat"] = "kong/router/compat.lua",
+    ["kong.router.expressions"] = "kong/router/expressions.lua",
+    ["kong.router.atc"] = "kong/router/atc.lua",
+    ["kong.router.fields"] = "kong/router/fields.lua",
+    ["kong.router.utils"] = "kong/router/utils.lua",
+
     ["kong.conf_loader"] = "kong/conf_loader/init.lua",
     ["kong.conf_loader.listeners"] = "kong/conf_loader/listeners.lua",