refactor(path): path_has_wildcard() #40893

Problem:
Redundant code.

Solution:
Combine path_has_wildcard() and path_has_exp_wildcard(). They have similar logic.
Also, the latter operates on whatever wildcards remain after shell/env/backtick
expansion, so the two felt somewhat related.

Also drop some unnecessary MB_PTR_ADV calls.

test/functional/vimscript/glob_spec.lua

@@ -4,6 +4,7 @@ local n = require('test.functional.testnvim')()
 local describe, it, before_each, after_each = t.describe, t.it, t.before_each, t.after_each
 local clear, command, eval, eq = n.clear, n.command, n.eval, t.eq
 local mkdir = t.mkdir
+local fn = n.fn
 
 before_each(function()
   clear()
@@ -29,3 +30,33 @@ describe('glob()', function()
     eq({}, eval("glob('*', 0, 1)"))
   end)
 end)
+
+describe('glob() with $ and ~ mixed with wildcards', function()
+  before_each(function()
+    clear()
+    mkdir('test-wild')
+    command('silent cd test-wild')
+    -- Names containing literal '$' and '~'.
+    command([[call writefile([], 'a$b.txt')]])
+    command([[call writefile([], 'a$c.txt')]])
+    mkdir('test-wild/d~e')
+    command([[call writefile([], 'd~e/f.txt')]])
+  end)
+
+  after_each(function()
+    n.rmdir('test-wild')
+  end)
+
+  it('$VAR is expanded before the trailing wildcard is globbed', function()
+    command('let $WILDDIR = "d~e"')
+    eq({ 'd~e/f.txt' }, eval([[glob('$WILDDIR/*', 0, 1)]]))
+  end)
+
+  it("wildcard descends through a component containing '~'", function()
+    eq({ 'd~e/f.txt' }, eval([[glob('d~e/*', 0, 1)]]))
+  end)
+
+  it("'~' mid-component combined with a wildcard", function()
+    eq({ 'd~e' }, eval([[glob('d~*', 0, 1)]]))
+  end)
+end)