use inferencebarrier instead of invokelatest for 1-arg @assert

This version would be better as per this comment: <#55739 (review)>
I confirmed this still allows us to avoid invalidations reported at
#55583.

base/error.jl

@@ -232,12 +232,14 @@ macro assert(ex, msgs...)
         msg = msg # pass-through
     elseif !isempty(msgs) && (isa(msg, Expr) || isa(msg, Symbol))
         # message is an expression needing evaluating
-        msg = :(Main.Base.invokelatest(Main.Base.string, $(esc(msg))))
+        # N.B. To reduce the risk of invalidation caused by the complex callstack involved
+        # with `string`, use `inferencebarrier` here to hide this `string` from the compiler.
+        msg = :(Main.Base.inferencebarrier(Main.Base.string)($(esc(msg))))
     elseif isdefined(Main, :Base) && isdefined(Main.Base, :string) && applicable(Main.Base.string, msg)
         msg = Main.Base.string(msg)
     else
         # string() might not be defined during bootstrap
-        msg = :(Main.Base.invokelatest(_assert_tostring, $(Expr(:quote,msg))))
+        msg = :(Main.Base.inferencebarrier(_assert_tostring)($(Expr(:quote,msg))))
     end
     return :($(esc(ex)) ? $(nothing) : throw(AssertionError($msg)))
 end

base/strings/string.jl

@@ -208,7 +208,7 @@ end
             i = i′
             @inbounds l = codeunit(s, i)
             (l < 0x80) | (0xf8 ≤ l) && return i+1
-            @assert l >= 0xc0 "invalid codeunit"
+            @assert l >= 0xc0
         end
         # first continuation byte
         (i += 1) > n && return i