[NFC] Update .swiftformat config for consistency (#6122)

`UserToolchain.swift` was formatted by `swift-format` with a config that's inconsistent with `.swiftformat` committed in the repository, primarily in its use of 2-space indentation.

Reverted the commit that applies `swift-format`. Also updated `.swiftformat` with more tweaks that codify conventions already established in our repository. Applied new rules to `UserToolchain.swift`

Author: MaxDesiatov

.swiftformat

@@ -1,15 +1,43 @@
-# file options
+## File options
 
 --swiftversion 5.5
 --exclude .build
 
-# format options
+## Formatting options
 
---self insert
---patternlet inline
---stripunusedargs unnamed-only
+# Configure the placement of an extension's access control keyword.
+--extensionacl on-declarations
+
+# #if indenting
 --ifdef no-indent
+
+# Wrap lines that exceed the specified maximum width.
 --maxwidth 120
---extensionacl on-declarations
 
-# rules
+# Reposition `let` or `var` bindings within pattern.
+--patternlet inline
+
+# Insert explicit `self` where applicable.
+--self insert
+
+# Mark unused function arguments with `_`.
+--stripunusedargs unnamed-only
+
+# Remove trailing space at end of a line.
+--trimwhitespace always
+
+# Wrap `@attributes` onto a separate line.
+--funcattributes prev-line
+--typeattributes prev-line
+--varattributes prev-line
+
+# Use `Void` for type declarations and `()` for values.
+--voidtype void
+
+# Align wrapped function arguments or collection elements.
+--wraparguments before-first
+
+## Rules
+
+# Prefer `&&` over `,` comma in `if`, `guard` or `while` conditions.
+--disable andOperator