[vm/file/win] Normalize absolute paths before adding long-prefix.

Long-prefixed paths can't have '..' segments in them.

Delete recursively uses long-prefixes, so the tests that verify long paths handling had to be updated accordingly: it's okay to use long paths when they are prefixed(when they are deleted recursively).

This is follow-up to https://github.com/dart-lang/sdk/commit/4928998ebe7d45ca27846af1e8cd4fd45cd475e3

Bug: https://github.com/dart-lang/sdk/issues/56125
Change-Id: I6613b1a324e8923d05e5f0a470ee5b2999d1b929
TEST=ci
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/374220
Commit-Queue: Alexander Aprelev <aam@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>

https://dart.googlesource.com/sdk/+/b207aed8b7f45e5ed3c515e9c8da8aca56cc4240

DEPS

diff --git a/DEPS b/DEPS
index b418f59..55f9d59 100644
--- a/DEPS
+++ b/DEPS
@@ -282,7 +282,7 @@
 
   'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + 'c5c0c54d6d1da3ddf45a6a527b57310d1283b897',
 
-  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '000149860ffc8a60dec57d003ed2a9430ce7567e',
+  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'b207aed8b7f45e5ed3c515e9c8da8aca56cc4240',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '348fdeebb31496f6bb10c576d6d973748b422a8f',
 

commits.json

diff --git a/commits.json b/commits.json
index 212f59c..0a0c97e 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"c5c0c54d6d1da3ddf45a6a527b57310d1283b897",
-  "engine/src/flutter/third_party/dart":"000149860ffc8a60dec57d003ed2a9430ce7567e",
+  "engine/src/flutter/third_party/dart":"b207aed8b7f45e5ed3c515e9c8da8aca56cc4240",
   "flutter":"348fdeebb31496f6bb10c576d6d973748b422a8f"
 }
\ No newline at end of file