Revert "Partially reland Auto-generate v8 version based on tags."

This reverts commit 0707afc8.

Revert "Ensure tags are fetched when generating the V8 version."

This reverts commit ea6831e9.

Revert "Restrict tag-update for version generation to cached git repos."

This reverts commit c6641e13.

BUG=chromium:446166
LOG=n

Review URL: https://codereview.chromium.org/866263005

Cr-Commit-Position: refs/heads/master@{#26244}