Speed up enry.IsVendor (#15213)

`enry.IsVendor` is kinda slow as it simply iterates across all regexps.
This PR ajdusts the regexps to combine them to make this process a
little quicker.

Related #15143

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/analyze/vendor_test.go

@@ -0,0 +1,42 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package analyze
+
+import "testing"
+
+func TestIsVendor(t *testing.T) {
+	tests := []struct {
+		path string
+		want bool
+	}{
+		{"cache/", true},
+		{"random/cache/", true},
+		{"cache", false},
+		{"dependencies/", true},
+		{"Dependencies/", true},
+		{"dependency/", false},
+		{"dist/", true},
+		{"dist", false},
+		{"random/dist/", true},
+		{"random/dist", false},
+		{"deps/", true},
+		{"configure", true},
+		{"a/configure", true},
+		{"config.guess", true},
+		{"config.guess/", false},
+		{".vscode/", true},
+		{"doc/_build/", true},
+		{"a/docs/_build/", true},
+		{"a/dasdocs/_build-vsdoc.js", true},
+		{"a/dasdocs/_build-vsdoc.j", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			if got := IsVendor(tt.path); got != tt.want {
+				t.Errorf("IsVendor() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}