This adds a bunch of assertions to CSA, mostly about documenting and checking
parameter types.

Drive-by-change: Removed unused function.

BUG=v8:6325

Review-Url: https://codereview.chromium.org/2847923003
Cr-Original-Original-Commit-Position: refs/heads/master@{#45398}
Committed: https://chromium.googlesource.com/v8/v8/+/b14a981496ad1f841683479d2f9188dfa2d6b4bd
Review-Url: https://codereview.chromium.org/2847923003
Cr-Original-Commit-Position: refs/heads/master@{#45443}
Committed: https://chromium.googlesource.com/v8/v8/+/62b0de1ef53816d6dae3fa519a846f942b701dda
Review-Url: https://codereview.chromium.org/2847923003
Cr-Commit-Position: refs/heads/master@{#45607}