v8: backport header diff from da5b745dba387

Backport deprecation of `Context::EstimatedSize()` from
da5b745dba387 (“[api] deprecate unused context size estimate”).

Ref: https://github.com/v8/v8/commit/da5b745dba387d0afdb99cd385ba1467a3ca2831

PR-URL: https://github.com/nodejs/node/pull/12875


Reviewed-By: James M Snell <jasnell@gmail.com>