Expand free alias types when computing implied outlives-bounds

[fmease]

Supersedes #122340 (see lengthy discussions in comments).
Follow-up to #119350.

Draft status: Need to add more tests, will do later — am at conf. Also: Needs better PR descr.

r? oli-obk

[rust-log-analyzer]

The job x86_64-gnu-llvm-19 failed! Check out the build log: (web) (plain)

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#18 exporting to docker image format
#18 sending tarball 20.3s done
#18 DONE 27.8s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-19]
[CI_JOB_NAME=x86_64-gnu-llvm-19]
debug: `DISABLE_CI_RUSTC_IF_INCOMPATIBLE` configured.
---
sccache: Listening on address 127.0.0.1:4226
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-19', '--enable-llvm-link-shared', '--set', 'rust.randomize-layout=true', '--set', 'rust.thin-lto-import-instr-limit=10', '--set', 'build.print-step-timings', '--enable-verbose-tests', '--set', 'build.metrics', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--set', 'rust.lld=false', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--set', 'gcc.download-ci-gcc=true', '--enable-new-symbol-mangling']
configure: build.build          := x86_64-unknown-linux-gnu
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-19/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.randomize-layout := True
configure: rust.thin-lto-import-instr-limit := 10
---
test [ui] tests/ui/wrong-hashset-issue-42918.rs ... ok

failures:

---- [ui] tests/ui/lazy-type-alias/implied-outlives-bounds-1.rs#print stdout ----
Saved the actual stderr to "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/lazy-type-alias/implied-outlives-bounds-1.print/implied-outlives-bounds-1.print.stderr"
diff of stderr:

1 error: rustc_outlives
-   --> $DIR/implied-outlives-bounds-1.rs:16:1
+   --> $DIR/implied-outlives-bounds-1.rs:13:1
3    |
4 LL | struct Type<'a, K, V>(&'a mut Alias<K, V>);
5    | ^^^^^^^^^^^^^^^^^^^^^

Note: some mismatched output was normalized before being compared
-   --> /checkout/tests/ui/lazy-type-alias/implied-outlives-bounds-1.rs:13:1
+   --> $DIR/implied-outlives-bounds-1.rs:13:1
---
To only update this specific test, also pass `--test-args lazy-type-alias/implied-outlives-bounds-1.rs`

error in revision `print`: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/lazy-type-alias/implied-outlives-bounds-1.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--cfg" "print" "--check-cfg" "cfg(test,FALSE,default,print)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/lazy-type-alias/implied-outlives-bounds-1.print" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error: rustc_outlives
##[error]  --> /checkout/tests/ui/lazy-type-alias/implied-outlives-bounds-1.rs:13:1
   |
LL | struct Type<'a, K, V>(&'a mut Alias<K, V>); //[print]~ ERROR rustc_outlives
   | ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: K: 'a
   = note: V: 'a

error: aborting due to 1 previous error
------------------------------------------