On Windows PowerShell, defer Add-Type until Set-ConsoleMode executed

[rkeithhill]

On PS Core, do not set the console mode at all.
PS Core, since the release of 6.0.0 has handled setting/resetting the
console mode, so no need for posh-git to do this. See:
PowerShell/PowerShell#2991

This speeds up module import by ~.5 to .7 seconds on PSCore and by
~150-200 msecs on Windows PowerShell.

Fix #637 and maybe #635

[rkeithhill]

Here's some profiling data.

Current perf (without this PR):

WARNING: CheckRequirements.ps1 load time: 89
WARNING: ConsoleMode.ps1 load time: 930 <<< ~1 second here!!!
WARNING: Utils.ps1 load time: 136
WARNING: AnsiUtils.ps1 load time: 34
WARNING: WindowTitle.ps1 load time: 8
WARNING: PoshGitTypes.ps1 load time: 28
WARNING: GitUtils.ps1 load time: 37
WARNING: GitPrompt.ps1 load time: 90
WARNING: GitParamTabExpansion.ps1 load time: 35
WARNING: GitTabExpansion.ps1 load time: 140
WARNING: TortoiseGit.ps1 load time: 10
WARNING: Process through configuring prompt func: 27
WARNING: Process through end: 5
WARNING: Total pms1 import time: 1592
Loading personal and system profiles took 2672ms.
C:\Users\Keith
11-02 23:08:00 232ms 1> << note that prompt processing time is pretty short

Now with just deferring the Add-Type until first use - which happens to be in the first call to Write-VcsStatus which happens the first time the prompt function is called:

WARNING: CheckRequirements.ps1 load time: 90
WARNING: ConsoleMode.ps1 load time: 32  <<< Wow! this is much better
WARNING: Utils.ps1 load time: 154
WARNING: AnsiUtils.ps1 load time: 33
WARNING: WindowTitle.ps1 load time: 8
WARNING: PoshGitTypes.ps1 load time: 29
WARNING: GitUtils.ps1 load time: 38
WARNING: GitPrompt.ps1 load time: 102
WARNING: GitParamTabExpansion.ps1 load time: 33
WARNING: GitTabExpansion.ps1 load time: 150
WARNING: TortoiseGit.ps1 load time: 18
WARNING: Process through configuring prompt func: 30
WARNING: Process through end: 5
WARNING: Total pms1 import time: 745
Loading personal and system profiles took 1817ms.  <<< Profile load time looks better
C:\Users\Keith
11-02 23:11:08 1044ms 1>   <<< But we played a shell game and move the time here  232 > 1044 ms

Now with not using Set-ConsoleMode on PS Core on Windows in a standard ConsoleHost (here we come out pretty good all around):

WARNING: CheckRequirements.ps1 load time: 90
WARNING: ConsoleMode.ps1 load time: 25  <<< Good!
WARNING: Utils.ps1 load time: 147
WARNING: AnsiUtils.ps1 load time: 31
WARNING: WindowTitle.ps1 load time: 8
WARNING: PoshGitTypes.ps1 load time: 34
WARNING: GitUtils.ps1 load time: 41
WARNING: GitPrompt.ps1 load time: 104
WARNING: GitParamTabExpansion.ps1 load time: 30
WARNING: GitTabExpansion.ps1 load time: 136
WARNING: TortoiseGit.ps1 load time: 11
WARNING: Process through configuring prompt func: 30
WARNING: Process through end: 6
WARNING: Total pms1 import time: 714
Loading personal and system profiles took 1840ms.
C:\Users\Keith
11-02 23:14:13 221ms 1>  <<< Good!

One thing I've noted is there is a significant stddev in the GitTabExpansion processing time. I've seen it range from 136 up to 499 ms. That might be good place to look next for module import perf improvements.

[dahlbyk]

This seems like a future extensibility point for other hosts that don't need Set-ConsoleMode, but this is good for now.

[musm]

when will this be available in the beta?

[dahlbyk]

I still have a few lingering PRs to catch up with, but I'll try to ship a new beta in the next week or so.

[dahlbyk]

I'll try to ship a new beta in the next week or so.

So, uh. Beta 3 shipped yesterday. 🙄

[dahlbyk]

@rkeithhill What's the advantage of splitting this into begin/end?

[rkeithhill]

In this particular case, there is no advantage. Then again, there is no harm either. But I can simplify this if you'd like.

[dahlbyk]

No change necessary unless you find the alternative easier to read. Just curious if I was missing something.