Name the macro slot count

Three loops walked 1..36 by hand, two of them re-arguing in comments why 36
is the right number. It is: the client addresses 18 account-wide macros at
1-18 and 18 character-specific ones at 19-36, and that range is what
GetMacroInfo and C_Macro.SetMacroDisplay index. Nothing in the API hands it
back -- GetNumMacros() returns how many of each tab are used, which cannot be
summed into a range, because the character block still starts at 19 when the
account block is empty. Blizzard's MAX_MACROS is no better: it lives in the
load-on-demand Blizzard_MacroUI and is nil until the macro window is opened.

So CleveRoids.MAX_MACRO_SLOTS in Init.lua, carrying that reasoning once.
ValidateAllMacros also dropped a numAccountMacros it computed and never read.

ReleaseDisplays keeps sweeping the full range rather than the macros it knows
it published: PublishAllDisplays clears that record on each re-parse, so a
macro claimed before one and gone after it would keep our last published value
forever. Releasing a slot we never claimed costs nothing, and it runs once.

Extensions/MacroErrorUI.lua

@@ -1180,7 +1180,7 @@ local function ReportAllMacroErrors()
 
     -- Collect body (syntax) errors per macro. Macro names are no longer
     -- restricted (slot/index-based identification), so no name checks here.
-    for i = 1, 36 do
+    for i = 1, CleveRoids.MAX_MACRO_SLOTS do
         local nameOk, name = pcall(GetMacroInfo, i)
         if nameOk and name and name ~= "" then
             local errors = {}