When user specifies both --runtimes and --corerun the Runtime printed for CoreRun job is invalid

[adamsitnik]

With #2002 we made it possible to mix --runtimes and --corerun, with #1621 we started hiding the Job and Toolchain columns.

Repro:

dotnet run -c Release -f net6.0 -- -filter *IntroDisassembly.* --runtimes net6.0 net7.0 --corerun D:\projects\runtime\artifacts\bin\testhost\net7.0-windows-Debug-x64\shared\Microsoft.NETCore.App\8.0.0\corerun.exe --job dry

BenchmarkDotNet=v0.13.2.20220901-develop, OS=Windows 11 (10.0.22000.856/21H2)
AMD Ryzen Threadripper PRO 3945WX 12-Cores, 1 CPU, 24 logical and 12 physical cores
.NET SDK=7.0.100-rc.1.22423.16
  [Host]     : .NET 6.0.8 (6.0.822.36306), X64 RyuJIT AVX2
  Job-MFIBNO : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT AVX2
  Job-UPJICA : .NET 6.0.8 (6.0.822.36306), X64 RyuJIT AVX2
  Job-QIGXWB : .NET 7.0.0 (7.0.22.42223), X64 RyuJIT AVX2

Method	Runtime	Mean	Error	Ratio	Code Size
SumLocal	.NET 6.0	255.2 us	NA	1.00	49 B
SumLocal	.NET 6.0	255.8 us	NA	1.00	35 B
SumLocal	.NET 7.0	258.3 us	NA	1.01	49 B
SumField	.NET 6.0	264.3 us	NA	0.95	139 B
SumField	.NET 6.0	279.4 us	NA	1.00	67 B
SumField	.NET 7.0	264.9 us	NA	0.95	139 B

As you can see, we BDN is currently printing .NET 6.0 for the CoreRun job (most likely because it was build targeting net6.0 tfm). This is wrong. In such case it should contain something like "local build". In case of multiple runtimes and multiple coreruns provided, we should just display the job column id (#1621)

Reported offline by @bartonjs