v6.0.0-beta.8 release of PowerShellCore

Here are the major changes:

* Breaking changes

- Changed `New-Service` to return error when given unsupported `-StartupType` and fixed `Set-Service` icon failing test. (#4802)
- Allow `*` to be used in registry path for `Remove-Item`. (#4866)
- Remove unsupported `-ShowWindow` switch from `Get-Help`. (#4903)
- Fix incorrect position of a parameter which resulted in the args passed as input instead of as args for `InvokeScript()`. (#4963)

* Engine updates and fixes

- Make calls to `void CodeMethod` work. (#4850) (Thanks @powercode)
- Get `PSVersion` and `GitCommitId` from the `ProductVersion` attribute of assembly (#4863) (Thanks @iSazonov)
- Fix `powershell -version` and built-in help for `powershell.exe` to align with other native tools. (#4958 & #4931) (Thanks @iSazonov)
- Load assemblies with `Assembly.LoadFrom` before `Assembly.Load` when the file path is given. (#4196)
- Add a generic file watcher function in `HelpersCommon.psm1`. (#4775)
- Update old links and fix broken links in `docs/host-powershell/README.md`. (#4877)
- Fix when importing remote modules using version filters (and added tests). (#4900)
- Enable transcription of native commands on non-Windows platforms. (#4871)
- Add a new line to `CommandNotFoundException` error string. (#4934 & #4991)
- Fix bug where PowerShell would exit with an error within an SSH remoting connection on Linux. (#4993)
- Fix issues with expression redirected to file. (#4847)

* General cmdlet updates and fixes

- Added `Remove-Service` to Management module. (#4858) (Thanks @joandrsn)
- Added functionality to set credentials on `Set-Service` command. (#4844) (Thanks @joandrsn)
- Fix `Select-String` to exclude directories (as opposed to individual files) discovered from `-Path`. (#4829) (Thanks @iSazonov)
- `Get-Date` now supports more argument completion scenarios by adding `ArgumentCompletionsAttribute`. (#4835) (Thanks @iSazonov)
- Exclude `-ComObject` parameter of `New-Object` on unsupported (currently non-Windows) platforms. (#4922) (Thanks @iSazonov)
- Updated default `ModuleVersion` in `New-ModuleManifest` to `0.0.1` to align with SemVer. (#4842) (Thanks @LDSpits)
- Add Multipart support to web cmdlets. (#4782) (Thanks @markekraus)
- Add `-ResponseHeadersVariable` to `Invoke-RestMethod` to enable the capture of response headers. (#4888) (Thanks @markekraus)
- Initialize web cmdlets headers dictionary only once. (#4853) (Thanks @markekraus)
- Change web cmdlets `UserAgent` from `WindowsPowerShell` to `PowerShell`. (#4914) (Thanks @markekraus)

* DSC Language

- Update version of `PSDesiredStateConfiguration` in project files to fix complication of MOF files with the `Configuration` keyword. (#4979)
