rustdoc: fix caching of intra-doc links on reexports

[lolbinarycat]

previously two reexports of the same item would share a set of intra-doc links, which would cause problems if they had two different links with the same text. this was fixed by using the reexport defid as the key, if it is available.

fixes #144965

[rustbot]

r? @GuillaumeGomez

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[GuillaumeGomez]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit 34b358d with merge 310f62e…

To cancel the try build, run the command @bors try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 310f62e (310f62e6ca6b940010d226efa0707077848526b7, parent: 213d946a384b46989f6fd9c8ae9c547b4e354455)

[rust-timer]

Finished benchmarking commit (310f62e): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary 2.3%, secondary -4.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.5%	[-6.5%, -2.5%]	2
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Cycles

Results (secondary -3.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-3.3%, -2.8%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 470.023s -> 468.852s (-0.25%)
Artifact size: 377.52 MiB -> 377.48 MiB (-0.01%)

[GuillaumeGomez]

Seems like there is no perf change at all.