perf: use HashSet<char> and String.exists for adorner detection in TextConversions

Two small improvements to TextConversions.RemoveAdorners:

1. Switch DefaultRemovableAdornerCharacters from F# Set<char> (O(log n) lookup)
   to System.Collections.Generic.HashSet<char> (O(1) lookup). The set has ~26
   characters; while individual operations are fast, this function is called on
   every cell when parsing CSV/JSON/XML for AsInteger, AsDecimal, AsInteger64.

2. Replace the manual mutable-flag loop with String.exists, which short-circuits
   on the first adorner match. The previous loop always iterated to the end even
   after finding an adorner. For values like ',234' the adorner is at index 0,
   so early exit skips 5 unnecessary iterations.

No API change — DefaultRemovableAdornerCharacters is private. The public
DefaultNonCurrencyAdorners and DefaultCurrencyAdorners members remain Set<char>.
All 2896 tests pass.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/FSharp.Data.Runtime.Utilities/TextConversions.fs

@@ -5,6 +5,7 @@
 namespace FSharp.Data
 
 open System
+open System.Collections.Generic
 open System.Globalization
 open System.Text.RegularExpressions
 
@@ -85,21 +86,21 @@ type TextConversions private () =
         |> Set.ofArray
 
     static member val private DefaultRemovableAdornerCharacters =
-        Set.union TextConversions.DefaultNonCurrencyAdorners TextConversions.DefaultCurrencyAdorners
+        // HashSet<char> for O(1) membership testing (vs O(log n) for F# Set)
+        HashSet<char>(Set.union TextConversions.DefaultNonCurrencyAdorners TextConversions.DefaultCurrencyAdorners)
 
     //This removes any adorners that might otherwise cause the inference to infer string. A notable a change is
     //Currency Symbols are now treated as an Adorner like a '%' sign thus are now independent
     //of the culture. Which is probably better since we have lots of scenarios where we want to
     //consume values prefixed with € or $ but in a different culture.
     static member private RemoveAdorners(value: string) =
-        // Fast path: check if any adorners exist before doing expensive operations
-        let mutable hasAdorners = false
-
-        for i = 0 to value.Length - 1 do
-            if TextConversions.DefaultRemovableAdornerCharacters.Contains(value.[i]) then
-                hasAdorners <- true
-
-        if not hasAdorners then
+        // Fast path: short-circuit on first adorner found (String.exists stops early)
+        if
+            not (
+                value
+                |> String.exists (fun c -> TextConversions.DefaultRemovableAdornerCharacters.Contains(c))
+            )
+        then
             // No adorners found, return original string to avoid allocation
             value
         else