RFR: 8357086: os::xxx functions returning memory size should return size_t [v9]

[Anton Artemov]

> Hi,
> 
> in this PR the output value type for functions which return memory are changed, namely:
> 
> 
> static julong available_memory(); --> static size_t available_memory();
> static julong used_memory(); --> static size_t used_memory();
> static julong free_memory(); --> static size_t free_memory(); 
> static jlong total_swap_space(); --> static ssize_t total_swap_space();
> static jlong free_swap_space(); --> static ssize_t free_swap_space(); 
> static julong physical_memory(); --> static size_t physical_memory(); 
> 
> 
> The changes are done so that the other parts of the code have minimal impact. 
> Tested in GHA and Tiers 1-4.

Anton Artemov has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 17 commits:

 - 8357086: Fixed merge conflict.
 - 8357086: Changed returm type to struct.
 - 8357086: Return size_t from swap mem funcs, added checks.
 - 8357086: Added missed casts.
 - 8357086: Changed return type for total_swap_space and free_swap_space to ssize_t
 - Merge remote-tracking branch 'origin/master' into JDK-8357086_size_t_memfuncs
 - 8357086: Fixed spaces in formatting in gc-related code.
 - 8357086: Fixed formatting.
 - 8357086: Addressed reviewer's comments.
 - 8357086: More work.
 - ... and 7 more: https://git.openjdk.org/jdk/compare/e18277b4...dd9275ca

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Changes: https://git.openjdk.org/jdk/pull/25450/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25450&range=08
  Stats: 247 lines in 22 files changed: 88 ins; 1 del; 158 mod
  Patch: https://git.openjdk.org/jdk/pull/25450.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25450/head:pull/25450

PR: https://git.openjdk.org/jdk/pull/25450