[InstCombine] PHI-of-extractvalues -> extractvalue-of-PHI, aka invokes are bad

While since D86306 we do it's sibling fold for `insertvalue`,
we should also do this for `extractvalue`'s.

And unlike that one, the results here are, quite honestly, shocking,
as it can be observed here on vanilla llvm test-suite + RawSpeed results:

```
| statistic name                                     | baseline  | proposed  |       Δ |       % |    |%| |
|----------------------------------------------------|-----------|-----------|--------:|--------:|-------:|
| asm-printer.EmittedInsts                           | 7945095   | 7942507   |   -2588 |  -0.03% |  0.03% |
| assembler.ObjectBytes                              | 273209920 | 273069800 | -140120 |  -0.05% |  0.05% |
| early-cse.NumCSE                                   | 2183363   | 2183398   |      35 |   0.00% |  0.00% |
| early-cse.NumSimplify                              | 541847    | 550017    |    8170 |   1.51% |  1.51% |
| instcombine.NumAggregateReconstructionsSimplified  | 2139      | 108       |   -2031 | -94.95% | 94.95% |
| instcombine.NumCombined                            | 3601364   | 3635448   |   34084 |   0.95% |  0.95% |
| instcombine.NumConstProp                           | 27153     | 27157     |       4 |   0.01% |  0.01% |
| instcombine.NumDeadInst                            | 1694521   | 1765022   |   70501 |   4.16% |  4.16% |
| instcombine.NumPHIsOfExtractValues                 | 0         | 37546     |   37546 |   0.00% |  0.00% |
| instcombine.NumSunkInst                            | 63158     | 63686     |     528 |   0.84% |  0.84% |
| instcount.NumBrInst                                | 874304    | 871857    |   -2447 |  -0.28% |  0.28% |
| instcount.NumCallInst                              | 1757657   | 1758402   |     745 |   0.04% |  0.04% |
| instcount.NumExtractValueInst                      | 45623     | 11483     |  -34140 | -74.83% | 74.83% |
| instcount.NumInsertValueInst                       | 4983      | 580       |   -4403 | -88.36% | 88.36% |
| instcount.NumInvokeInst                            | 61018     | 59478     |   -1540 |  -2.52% |  2.52% |
| instcount.NumLandingPadInst                        | 35334     | 34215     |   -1119 |  -3.17% |  3.17% |
| instcount.NumPHIInst                               | 344428    | 331116    |  -13312 |  -3.86% |  3.86% |
| instcount.NumRetInst                               | 100773    | 100772    |      -1 |   0.00% |  0.00% |
| instcount.TotalBlocks                              | 1081154   | 1077166   |   -3988 |  -0.37% |  0.37% |
| instcount.TotalFuncs                               | 101443    | 101442    |      -1 |   0.00% |  0.00% |
| instcount.TotalInsts                               | 8890201   | 8833747   |  -56454 |  -0.64% |  0.64% |
| instsimplify.NumSimplified                         | 75822     | 75707     |    -115 |  -0.15% |  0.15% |
| simplifycfg.NumHoistCommonCode                     | 24203     | 24197     |      -6 |  -0.02% |  0.02% |
| simplifycfg.NumHoistCommonInstrs                   | 48201     | 48195     |      -6 |  -0.01% |  0.01% |
| simplifycfg.NumInvokes                             | 2785      | 4298      |    1513 |  54.33% | 54.33% |
| simplifycfg.NumSimpl                               | 997332    | 1018189   |   20857 |   2.09% |  2.09% |
| simplifycfg.NumSinkCommonCode                      | 7088      | 6464      |    -624 |  -8.80% |  8.80% |
| simplifycfg.NumSinkCommonInstrs                    | 15117     | 14021     |   -1096 |  -7.25% |  7.25% |
```
... which tells us that this new fold fires whopping 38k times,
increasing the amount of SimplifyCFG's `invoke`->`call` transforms by +54% (+1513) (again, D85787 did that last time),
decreasing total instruction count by -0.64% (-56454),
and sharply decreasing count of `insertvalue`'s (-88.36%, i.e. 9 times less)
and `extractvalue`'s (-74.83%, i.e. four times less).

This causes geomean -0.01% binary size decrease
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=size-text
and, ignoring `O0-g`, is a geomean -0.01%..-0.05% compile-time improvement
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=instructions

The other thing that tells is, is that while this is a massive win for `invoke`->`call` transform
`InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse()` fold,
which is supposed to be dealing with such aggregate reconstructions,
fires a lot less now. There are two reasons why:
1. After this fold, as it can be seen in tests, we may (will) end up with trivially redundant PHI nodes.
   We don't CSE them in InstCombine presently, which means that EarlyCSE needs to run and then InstCombine rerun.
2. But then, EarlyCSE not only manages to fold such redundant PHI's,
   it also sees that the extract-insert chain recreates the original aggregate,
   and replaces it with the original aggregate.

The take-aways are
1. We maybe should do most trivial, same-BB PHI CSE in InstCombine
2. I need to check if what other patterns remain, and how they can be resolved.
   (i.e. i wonder if `foldAggregateConstructionIntoAggregateReuse()` might go away)

This is a reland of the original commit fcb51d8c,
because originally i forgot to ensure that the base aggregate types match.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D86530