patch 9.1.0769: filetype: MLIR files are not recognized

Problem:  filetype: MLIR files are not recognized
Solution: Detect '*.mlir' files as mlir filetype,
          include a mlir filetype plugin
          (Wu, Zhenyu)

closes: #15826

Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -479,6 +479,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     mgp: ['file.mgp'],
     mib: ['file.mib', 'file.my'],
     mix: ['file.mix', 'file.mixal'],
+    mlir: ['file.mlir'],
     mma: ['file.nb', 'file.wl'],
     mmp: ['file.mmp'],
     modconf: ['/etc/modules.conf', '/etc/modules', '/etc/conf.modules', '/etc/modprobe.file', 'any/etc/conf.modules', 'any/etc/modprobe.file', 'any/etc/modules', 'any/etc/modules.conf'],

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    769,
 /**/
     768,
 /**/