RFR: 8377895: Create sizeof_auto, to reduce narrowing conversions [v6]

[Leo Korinth]

> `sizeof_auto` is created so that we can reduce the amount of casting and thus make the code more type safe. The normal `sizeof` will return a `size_t` although the size of most stuff can be represented in a `uint8_t`. `sizeof_auto` will return the size in an as small unsigned type as is possible. The result is that expressions that uses `sizeof_auto` can convert to most integral types, and no explicit narrowing cast will be needed.
> 
> The change in `cpCache.hpp` is an example where we would get an implicit narrowing warning (if we had those enabled) using normal `sizeof`, but where `sizeof_auto` will not make the expression a `size_t` .

Leo Korinth has updated the pull request incrementally with one additional commit since the last revision:

  suggestion from Kim

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29716/files
  - new: https://git.openjdk.org/jdk/pull/29716/files/243316cb..49f37dc9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29716&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29716&range=04-05

  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29716.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29716/head:pull/29716

PR: https://git.openjdk.org/jdk/pull/29716