vim-patch:9.1.1360: filetype: GNU Radio companion files are not recognized

Problem:  filetype: GNU Radio companion files are not recognized
Solution: detect *.grc files as xml or yaml filetype depending on the
          first line (zeertzjq).

Ref:
- https://wiki.gnuradio.org/index.php/XML_GRC
- https://wiki.gnuradio.org/index.php/YAML_GRC

closes: vim/vim#17241

af4a5d6e2a

runtime/lua/vim/filetype.lua

@@ -1390,6 +1390,7 @@ local extension = {
   yaml = 'yaml',
   eyaml = 'yaml',
   mplstyle = 'yaml',
+  grc = detect_line1('<%?xml', 'xml', 'yaml'),
   yang = 'yang',
   yuck = 'yuck',
   z8a = 'z8a',

test/old/testdir/test_filetype.vim

@@ -1597,6 +1597,22 @@ func Test_git_file()
   filetype off
 endfunc
 
+func Test_grc_file()
+  filetype on
+
+  call writefile(['<?xml version="1.0"?>', '<block>', '</block>'], 'Xfile.grc')
+  split Xfile.grc
+  call assert_equal('xml', &filetype)
+  bwipe!
+
+  call writefile(['metadata:', '  file_format: 1'], 'Xfile.grc')
+  split Xfile.grc
+  call assert_equal('yaml', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 func Test_haredoc_file()
   filetype on
   call assert_true(mkdir('foo/bar', 'pR'))