Fixes #32556

Add a mechanism to be a customer of the extension host (share lifecycle) and begin reducing usage of IThreadService

* fix spelling of 'iff' and 'idenifier'

* Keep 'iff' in comment if it means *if and only if*

* Use r+ with truncation when saving existing files

'w' doesn't work with hidden files.

Fixes: https://github.com/Microsoft/vscode/issues/931

* use r+ only if EPERM is caught

* add check for Windows

* move writing to a separate method

* nits

* remove string overload for options

* remove encoding property from writeFileAndFlush

Fix #30181. If the tokenization has not be executed for lines above pasted area, we do not force tokenization info as we do not wait for the tokenization to complete.