[release] src/testUtils.ts: fix parsing of the compiler error file expansion

Build error output format can be different from the test output format.
Adjust the regex change in expandFilePathInOutput so it can capture
build errors that contain column numbers as well while capturing the
file path from test outputs such as

```
  TestB: b_test.go:6: test failed
```

The above line was incorrectly expanded in pre v0.16.0

pre v0.16.0: /^\s*(.+.go):(\d+):/
v0.16.0, v0.16.1: /\s+(\S+.go):(\d+):\s+/
this CL: /\s*(\S+\.go):(\d+):/

Fixes #522

Change-Id: Ifa8f07d3bb7c5aaa61d40dd29d9fae77d8ad0cbe
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/248737
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
Reviewed-by: Suzy Mueller <[email protected]>
(cherry picked from commit 1e4dbe2)
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/252118
TryBot-Result: kokoro <[email protected]>

Author: hyangah

src/testUtils.ts

@@ -486,7 +486,7 @@ export function cancelRunningTests(): Thenable<boolean> {
 function expandFilePathInOutput(output: string, cwd: string): string {
 	const lines = output.split('\n');
 	for (let i = 0; i < lines.length; i++) {
-		const matches = lines[i].match(/\s+(\S+.go):(\d+):\s+/);
+		const matches = lines[i].match(/\s*(\S+\.go):(\d+):/);
 		if (matches && matches[1] && !path.isAbsolute(matches[1])) {
 			lines[i] = lines[i].replace(matches[1], path.join(cwd, matches[1]));
 		}