Should ignore `.hs` and other source files under system temporary directory (those opened to view Git history etc.)

### Your environment
Output of `haskell-language-server --probe-tools` or `haskell-language-server-wrapper --probe-tools`:

```sh
haskell-language-server version: 1.4.0.0 (GHC: 8.10.4) (PATH: /Users/cyue/.ghcup/bin/haskell-language-server-wrapper-1.4.0) (GIT hash: 253547816ee216c53ee7dacc0ad3cac43e863d30)
Tool versions found on the $PATH
cabal: 3.2.0.0
stack: 2.7.3
ghc: 8.8.4
```
Which OS do you use:
MacOS

Which lsp-client do you use:
VSCode

Describe your project (alternative: link to the project):
*any*

Contents of `hie.yaml`:
N/A

### Steps to reproduce
Open [Git History] view
Select a commit
Locate a changed `.hs` file, click the [Previous] link to show diffs to previous version in editor

### Expected behaviour
Continue working as usual.

### Actual behaviour
Git plugin would create some `.hs` file from git history, within some folder under system TMP directory, and open it in editor.

HLS would then get triggered "indexing..." forever to figure out settings wrt such temp `.hs` files, normal IDE features like navigation and formatting will all pend execution. Even after all of the temp file editing tabs closed, and VSCode restarted, the "indexing..." status can not be avoided. Only after those temp files manually deleted, and VSCode restarted/reloaded, it can return to normal operations.

### Include debug information
N/A