Fix Get and Preview calls for local extensions

[shenglol]

The PR corrects the issue where Get and Preview operations were incorrectly calling Delete and CreateOrUpdate.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 10408762864)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 10408762864

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 10408762864"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 10408762864

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 10408762864"

[github-actions]

Dotnet Test Results

    72 files   -     36      72 suites   - 36   23m 28s ⏱️ - 10m 13s
11 039 tests  -     20  11 039 ✅  -     20  0 💤 ±0  0 ❌ ±0 
25 854 runs   - 12 923  25 854 ✅  - 12 923  0 💤 ±0  0 ❌ ±0 

Results for commit c174799. ± Comparison against base commit 4139b6c.