Stop keeping metadata in memory before writing it to disk
Fixes#96358
I created this PR according with the instruction given in the issue except for the following points:
- While the issue says "Write metadata into the temporary file in `encode_and_write_metadata` even if `!need_metadata_file`", I could not do that. That is because though I tried to do that and run `x.py test`, I got a lot of test failures as follows.
<details>
<summary>List of failed tests</summary>
<pre>
<code>
failures:
[ui] src/test/ui/json-multiple.rs
[ui] src/test/ui/json-options.rs
[ui] src/test/ui/rmeta/rmeta-rpass.rs
[ui] src/test/ui/save-analysis/emit-notifications.rs
[ui] src/test/ui/svh/changing-crates.rs
[ui] src/test/ui/svh/svh-change-lit.rs
[ui] src/test/ui/svh/svh-change-significant-cfg.rs
[ui] src/test/ui/svh/svh-change-trait-bound.rs
[ui] src/test/ui/svh/svh-change-type-arg.rs
[ui] src/test/ui/svh/svh-change-type-ret.rs
[ui] src/test/ui/svh/svh-change-type-static.rs
[ui] src/test/ui/svh/svh-use-trait.rs
test result: FAILED. 12915 passed; 12 failed; 100 ignored; 0 measured; 0 filtered out; finished in 71.41s
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu
Build completed unsuccessfully in 0:01:58
</code>
</pre>
</details>
- I could not resolve the extra tasks about `create_rmeta_file` and `create_compressed_metadata_file` for my lack of ability.
1ba1fec234