GHCup should fall back to older HLS version if I deny upgrading

**Is your feature request related to a problem? Please describe.**

VSCode starts: new HLS version! I don't want to upgrade right away, press "No" to the update, and then VSCode complains that HLS is not installed, although `ghcup list` lists an installed HLS version:
```
> ghcup list
[ Warn ] New ghc version available. To upgrade, run 'ghcup install ghc 9.2.2'
[ Warn ] New hls version available. To upgrade, run 'ghcup install hls 1.7.0.0'
Tool Version Tags Notes
...
✔✔ ghc 8.10.7 recommended,base-4.14.3.0 hls-powered
✗ ghc 9.0.1 base-4.15.0.0 hls-powered
✗ ghc 9.0.2 base-4.15.1.0 hls-powered
✓ ghc 9.2.1 base-4.16.0.0 hls-powered
✗ ghc 9.2.2 latest,base-4.16.1.0
...
✔✔ cabal 3.6.2.0 latest,recommended
...
✗ hls 1.6.0.0
✔✔ hls 1.6.1.0
✗ hls 1.7.0.0 latest,recommended
...
✓ stack 2.7.5 latest,recommended
✔✔ ghcup 0.1.17.7 latest,recommended
```

**Describe the solution you'd like**

GHCup should fallback to the installed version if I don't want to upgrade right away.

**Describe alternatives you've considered**

Users switch to `PATH` and don't let ghcup automatically handle the HLS installation.
I believe this feature is still in the scope of the automatic management solution.