Clean up CodepointWidthDetector (#14396)

My long-term plan is to replace the `CodepointWidth` enum with a simple integer
return value that indicates the amount of columns a codepoint is wide.
This is necessary so that we can return 0 for ZWJs (zero width joiners).

This initial commit represents a cleanup effort around `CodepointWidthDetector`.
Since less code runs faster, this change has the nice side-effect of running
roughly 5-10% faster across the board. It also drops the binary size by ~1.2kB.

## Validation Steps Performed
* `CodepointWidthDetectorTests` passes ✅
* U+26bf (``"`u{26bf}"`` inside pwsh) is a wide glyph
  in OpenConsole and narrow one in Windows Terminal ✅

tools/Generate-CodepointWidthsFromUCD.ps1

@@ -20,8 +20,8 @@
 # significantly smaller, which would provide a performance win on the admittedly
 # extremely rare occasion that we should need to regenerate our table.
 #
-# Invoke as ./Generate-xxx ucd.nounihan.flat.xml -Pack | Out-File -Encoding
-#           UTF-8 Temporary.cpp
+# Invoke this script from the root of this repository as:
+#   .\tools\Generate-CodepointWidthsFromUCD.ps1 -Path .\path\to\ucd.nounihan.flat.xml -OverridePath .\src\types\unicode_width_overrides.xml -Pack
 #
 # [1]: https://www.unicode.org/Public/UCD/latest/ucdxml/
 # [2]: https://www.unicode.org/reports/tr42/
@@ -43,15 +43,13 @@ Param(
     [string]$OverridePath = "overrides.xml",
 
     [switch]$Pack, # Pack tightly based on width
-    [switch]$NoOverrides, # Do not include overrides
-    [switch]$Full = $False # Include Narrow codepoints
+    [switch]$NoOverrides # Do not include overrides
 )
 
 Enum CodepointWidth {
     Narrow;
     Wide;
     Ambiguous;
-    Invalid;
 }
 
 # UCD Functions {{{
@@ -82,8 +80,8 @@ Function Get-UCDEntryWidth($entry) {
         "W"  { [CodepointWidth]::Wide; Return }
         "F"  { [CodepointWidth]::Wide; Return }
         "A"  { [CodepointWidth]::Ambiguous; Return }
+        default { throw "Unexpected East_Asian_Width property" }
     }
-    [CodepointWidth]::Invalid
 }
 
 Function Get-UCDEntryFlags($entry) {
@@ -224,20 +222,10 @@ $UCDRepertoire = $InputObject.ucd.repertoire.ChildNodes | Sort-Object {
     }
 }
 
-If (-not $Full) {
-    $UCDRepertoire = $UCDRepertoire | Where-Object {
-        # Select everything Wide/Ambiguous/Full OR Emoji w/ Emoji Presentation
-        ($_.ea -notin "N", "Na", "H") -or ($_.Emoji -eq "Y" -and $_.EPres -eq "Y")
-    }
-}
-
 $ranges = [UnicodeRangeList]::New(1024)
 
-$c = 0
 ForEach($v in $UCDRepertoire) {
     $range = [UnicodeRange]::new($v)
-    $c += $range.Length()
-
     If ($ranges.Count -gt 0 -and $ranges[$ranges.Count - 1].Merge($range)) {
         # Merged into last entry
         Continue
@@ -260,9 +248,16 @@ If (-not $NoOverrides) {
     }
 }
 
+$ranges.RemoveAll({ $args[0].Width -eq [CodepointWidth]::Narrow }) | Out-Null
+
+$c = 0
+ForEach($_ in $ranges) {
+    $c += $_.End - $_.Start + 1
+}
+
 # Emit Code
 "    // Generated by {0} -Pack:{1} -Full:{2} -NoOverrides:{3}" -f $MyInvocation.MyCommand.Name, $Pack, $Full, $NoOverrides
-"    // on {0} (UTC) from {1}." -f (Get-Date -AsUTC), $InputObject.ucd.description
+"    // on {0} from {1}." -f (Get-Date -AsUTC -Format "u"), $InputObject.ucd.description
 "    // {0} (0x{0:X}) codepoints covered." -f $c
 If (-not $NoOverrides) {
 "    // {0} (0x{0:X}) codepoints overridden." -f $overrideCount
@@ -270,11 +265,12 @@ If (-not $NoOverrides) {
 }
 "    static constexpr std::array<UnicodeRange, {0}> s_wideAndAmbiguousTable{{" -f $ranges.Count
 ForEach($_ in $ranges) {
+    $isAmbiguous = $_.Width -eq [CodepointWidth]::Ambiguous
     $comment = ""
     if ($null -ne $_.Comment) {
         # We only vend comments when we aren't packing tightly
         $comment = " // {0}" -f $_.Comment
     }
-"        UnicodeRange{{ 0x{0:x}, 0x{1:x}, CodepointWidth::{2} }},{3}" -f $_.Start, $_.End, $_.Width, $comment
+"        UnicodeRange{{ 0x{0:x}, 0x{1:x}, {2} }},{3}" -f $_.Start, $_.End, [int]$isAmbiguous, $comment
 }
 "    };"