Edit all-and-only applicable snippets to support $TM_SELECTED_TEXT,
where "applicable" is approximated by whether a snippet contains a
user-specified PowerShell expression, block, or body. Do not add,
remove, or otherwise change any placeholder number or name in order to
preserve backwards-compatibility.

Edit the following snippets (listed by name, not prefix):
- Class
- Constructor
- Method
- Enum
- Cmdlet
- Function-Advanced
- DSC Resource Provider (class-based)
- DSC Resource Provider (function-based)
- comment block
- do-until
- do-while
- while
- for
- for-reversed
- foreach
- function
- Function-Inline
- if
- elseif
- else
- switch
- try-catch
- try-catch-finally
- try-finally
- Workflow
- Workflow ForEachParallel
- Workflow InlineScript
- Workflow Parallel
- Workflow Sequence
- Region Block
- IfShouldProcess
- CalculatedProperty
- PesterDescribeContextIt
- PesterDescribeBlock
- PesterContextIt
- PesterContext
- PesterIt

* Define snippet named 'ArgumentCompleterAttribute with ScriptBlock'

* Define snippet named 'IArgumentCompleter Class'

* Define snippet named 'ArgumentCompleterAttribute ScriptBlock'

* Add script requirement directive snippets

Adds the following snippets (listed by name, not prefix):
- Requires Assembly
- Requires Assembly Path
- Requires Assembly Version
- Requires Module
- Requires Module RequiredVersion
- Requires Module Version
- Requires PSEdition
- Requires PSSnapin
- Requires PSSnapin Version
- Requires RunAsAdministrator
- Requires ShellId
- Requires Version

…global. (PowerShell#2035)

…the default branch (PowerShell#2037)

* add machine scope

* use a different setting for test and add user setting test

* remove isExecutable and remove powershell.developer.powerShellExePath