Reduce ExtensionManager memory allocations

[lahma]

TLDR; reduce test suite memory allocations by 40GB (> 90%).

I profiled tests run by OrchardCode suite to check if there's any easy wins to make them go faster. I was quite surprised by the memory allocation for the whole suite when run in Release mode, it was almost 44GB of memory allocated during the suite run.

After analysis I found out the ExtensionManager to be the culprit. It has a lot of closures and allocatey-LINQ usage + enumerators from interface use. Generally, I'd say it would be fine if done once but as it's repeated every time when system initializes in tests, it starts to cost.

I went through the code and made it less cool by using concrete types, more imperative constructs instead of LINQ and better equality lookups (feature id instead of feature object).

The test suite now allocates 40GB less during run and the ExtensionManager should be the same functionality-wise. This helps with the test suite performance and probably also with OrchardCore cold startup speed at least.

Relates to #12583

Before

After

[lahma]

Comparing to other PR "Deprecate ILuceneSearchQueryService in OrchardCore.Search.Lucene" which was run 11 hours ago and its run times, of course very unscientific because might have been different runner etc.

Other PR

Run dotnet test -c Release --no-restore --no-build ./test/OrchardCore.Tests/OrchardCore.Tests.csproj
Test run for /home/runner/work/OrchardCore/OrchardCore/test/OrchardCore.Tests/bin/Release/net6.0/OrchardCore.Tests.dll (.NETCoreApp,Version=v6.0)
Microsoft (R) Test Execution Command Line Tool Version 17.3.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
      No XML encryptor configured. Key {16ab46fb-abaa-44d6-[8](https://github.com/OrchardCMS/OrchardCore/actions/runs/3207591444/jobs/5242632583#step:6:9)e[9](https://github.com/OrchardCMS/OrchardCore/actions/runs/3207591444/jobs/5242632583#step:6:10)b-83480[12](https://github.com/OrchardCMS/OrchardCore/actions/runs/3207591444/jobs/5242632583#step:6:13)47b5e} may be persisted to storage in unencrypted form.

Passed!  - Failed:     0, Passed:   964, Skipped:     0, Total:   964, Duration: 1 m 7 s - /home/runner/work/OrchardCore/OrchardCore/test/OrchardCore.Tests/bin/Release/net6.0/OrchardCore.Tests.dll (net6.0)

This PR

Run dotnet test -c Release --no-restore --no-build ./test/OrchardCore.Tests/OrchardCore.Tests.csproj
Test run for /home/runner/work/OrchardCore/OrchardCore/test/OrchardCore.Tests/bin/Release/net6.0/OrchardCore.Tests.dll (.NETCoreApp,Version=v6.0)
Microsoft (R) Test Execution Command Line Tool Version 17.3.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
      No XML encryptor configured. Key {66fa1553-3[8](https://github.com/OrchardCMS/OrchardCore/actions/runs/3209629134/jobs/5246493936#step:6:9)b1-4f47-a4d6-[9](https://github.com/OrchardCMS/OrchardCore/actions/runs/3209629134/jobs/5246493936#step:6:10)9d4d[10](https://github.com/OrchardCMS/OrchardCore/actions/runs/3209629134/jobs/5246493936#step:6:11)d495c} may be persisted to storage in unencrypted form.

Passed!  - Failed:     0, Passed:   964, Skipped:     0, Total:   964, Duration: 24 s - /home/runner/work/OrchardCore/OrchardCore/test/OrchardCore.Tests/bin/Release/net6.0/OrchardCore.Tests.dll (net6.0)

[lahma]

Could I get hacktoberfest-accepted label for this PR as a reward, it seems to be available in the repo 🙏🏻

[Piedone]

Awesome!