Also: - drop no longer necessary quiche build workaround. - update build for boringssl's new location (since v0.29.0, it's no longer vendored) within the quiche tree. - move boringssl install dir out of quiche tree, and shorten it. Ref: https://github.com/cloudflare/quiche/issues/2277 Ref: https://github.com/cloudflare/quiche/pull/2278 Ref: #21620 Closes #21730