definitions: remove DefPathTable, merge index_to_key and def_path_hashes

[aerooneqq]

This PR removes DefPathTable and merges index_to_key with def_path_hashes as they are always updated together.

r? @petrochenkov

[petrochenkov]

@bors try @rust-timer queue

[aerooneqq]

Maybe need to restart perf, there were problems with github actions.
cc @petrochenkov

[petrochenkov]

@bors try cancel

[rust-bors]

Try build cancelled. Cancelled workflows:

[petrochenkov]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 29d6359 (29d635947db7a31f5b2a840c1b2dab059caebd46, parent: b7e97a98f24cdb1335850209991455cb9734d333)

[rust-timer]

Finished benchmarking commit (29d6359): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.0%, 0.8%]	21
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.3%, secondary -0.9%)

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

	mean	range	count
Regressions ❌ (primary)	3.3%	[3.3%, 3.3%]	1
Regressions ❌ (secondary)	2.1%	[1.3%, 3.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.0%	[-6.4%, -1.5%]	2
All ❌✅ (primary)	3.3%	[3.3%, 3.3%]	1

Cycles

Results (primary 2.1%, secondary -2.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 511.751s -> 510.109s (-0.32%)
Artifact size: 400.67 MiB -> 400.65 MiB (-0.00%)