Add ClangTidy check bugprone-bool-pointer-implicit-conversion.

------
https://clang.llvm.org/extra/clang-tidy/checks/bugprone-bool-pointer-implicit-conversion.html
Checks for conditions based on implicit conversion from a bool pointer to bool.

Example:

bool *p;
if (p) {
  // Never used in a pointer-specific way.
}

Change-Id: I9399469df2d2ea1980ed6d996430f0fd6631ff0c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307342
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
diff --git a/.clang-tidy b/.clang-tidy
index 9e1e026..9749799 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1 +1 @@
-Checks: '-*,bugprone-use-after-move,bugprone-unused-raii,bugprone-undelegated-constructor,bugprone-argument-comment,performance-for-range-copy,google-build-namespaces'
+Checks: '-*,bugprone-use-after-move,bugprone-unused-raii,bugprone-undelegated-constructor,bugprone-argument-comment,performance-for-range-copy,bugprone-bool-pointer-implicit-conversion,google-build-namespaces'