Implement vim.switchToInsertModeSelection command for switching selected text from visual mode to insert mode

[waynewaynetsai]

What this PR does / why we need it:

When we use 3rd party extension such as vscode surround, we can not handle there behavior easily.

But if we use 3rd party extension at insert mode, most of extensions will run correctly.

That's why we need vim.switchToInsertModeSelection command.

We can select words at visual mode, then switch visual mode selection to insert mode first.

After that, we can run 3rd party extension correctly and easily!

Side Effects:

• None

Which issue(s) this PR fixes

1. Feature Request Implement for [Feature request] Provide vim.switchToInsertModeSelection command for switching selected text from visual mode to insert mode #6773
2. Bug Solution for Can not edit inserted snippet correctly with vscode surround extension #6772
3. Workaround Solution for "Wrap with widget..." Quick fix doesn't select generated widget anymore Dart-Code/Dart-Code#3383 (comment)

[shadoath]

Looks pretty straight forward to me

[waynewaynetsai]

Looks pretty straight forward to me

Thanks for your review @shadoath! Since i'm the first time contributor, this PR still need a maintainer to approve running workflows.

[robersonliou]

Same issue here, hoping it could be merged as early as possible. :)

[waynewaynetsai]

I've refactor command handler with vscodevim's modeHandler for having similar coding style and implement test cases for single and multiple selection cases.

All vscodevim test cases have passed at my environment.

[ericlo23]

This command is quite useful.

[waynewaynetsai]

@J-Fields Would you mind giving me some advice?
If you could point me in the right direction, I can try to improve this pr or solving relative issues.