stdlib: Add @_disfavoredOverload to various functions for Embedded.

Functions like `fatalError()` have overloads for Embedded Swift only that take
StaticString instead of String, since String is unavailable. Unfortunately,
many of these overloads create the opportunity for ambiguity in certain
contexts. The easiest way to avoid the ambiguities is to mark each of the
overloads taking `String` as `@_disfavoredOverload`. Another approach that
could work would be to remove the default arguments from the `String` variants
in Embedded Swift only, but that would create even more duplication of source
code so it doesn't seem worth it.

Author: tshortli

stdlib/public/core/Assert.swift

@@ -39,6 +39,9 @@
 ///     is called.
 @_transparent
 @_unavailableInEmbedded
+#if $Embedded
+@_disfavoredOverload
+#endif
 public func assert(
   _ condition: @autoclosure () -> Bool,
   _ message: @autoclosure () -> String = String(),
@@ -99,6 +102,9 @@ public func assert(
 ///     `precondition(_:_:file:line:)` is called.
 @_transparent
 @_unavailableInEmbedded
+#if $Embedded
+@_disfavoredOverload
+#endif
 public func precondition(
   _ condition: @autoclosure () -> Bool,
   _ message: @autoclosure () -> String = String(),
@@ -162,6 +168,9 @@ public func precondition(
 @inlinable
 @inline(__always)
 @_unavailableInEmbedded
+#if $Embedded
+@_disfavoredOverload
+#endif
 public func assertionFailure(
   _ message: @autoclosure () -> String = String(),
   file: StaticString = #file, line: UInt = #line
@@ -221,6 +230,9 @@ public func assertionFailure(
 ///     line number where `preconditionFailure(_:file:line:)` is called.
 @_transparent
 @_unavailableInEmbedded
+#if $Embedded
+@_disfavoredOverload
+#endif
 public func preconditionFailure(
   _ message: @autoclosure () -> String = String(),
   file: StaticString = #file, line: UInt = #line
@@ -264,6 +276,9 @@ public func preconditionFailure(
 ///     line number where `fatalError(_:file:line:)` is called.
 @_transparent
 @_unavailableInEmbedded
+#if $Embedded
+@_disfavoredOverload
+#endif
 public func fatalError(
   _ message: @autoclosure () -> String = String(),
   file: StaticString = #file, line: UInt = #line