Userland: static vs non-static constexpr variables

Problem:
- `static` variables consume memory and sometimes are less
  optimizable.
- `static const` variables can be `constexpr`, usually.
- `static` function-local variables require an initialization check
  every time the function is run.

Solution:
- If a global `static` variable is only used in a single function then
  move it into the function and make it non-`static` and `constexpr`.
- Make all global `static` variables `constexpr` instead of `const`.
- Change function-local `static const[expr]` variables to be just
  `constexpr`.

Userland/Libraries/LibWeb/Cookie/ParsedCookie.cpp

@@ -5,6 +5,7 @@
  */
 
 #include "ParsedCookie.h"
+#include <AK/Array.h>
 #include <AK/StdLibExtras.h>
 #include <AK/Vector.h>
 #include <LibIPC/Decoder.h>
@@ -264,7 +265,7 @@ Optional<Core::DateTime> parse_date_time(StringView date_string)
     };
 
     auto parse_month = [&](StringView token) {
-        static const char* months[] { "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec" };
+        constexpr Array months { "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec" };
 
         for (unsigned i = 0; i < 12; ++i) {
             if (token.equals_ignoring_case(months[i])) {