src: apply clang-tidy rule bugprone-incorrect-roundings

[gengjiawen]

see https://clang.llvm.org/extra/clang-tidy/checks/bugprone-incorrect-roundings.html.

Checks the usage of patterns known to produce incorrect rounding. Programmers often use:

(int)(double_expression + 0.5)
to round the double expression to an integer. The problem with this:

It is unnecessarily slow.
It is incorrect. The number 0.499999975 (smallest representable float number below 0.5) rounds to 1.0. Even worse behavior for negative numbers where both -0.5f and -1.4f both round to 0.0.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/22166/