accept bare version as NuGet exact version for .NET tools

[JL03-Yue]

Customer Impact

In .NET 8 we made a breaking change that changes the current .NET tool installation mechanism from restore a local temporary project to downloading the .NET tool from NuGet. This change was introduced because this previous mechanism has number of side effects, often show up as flaky restore errors because MSBuild concepts like Directory.Build.props, or other heirarchical notions, pollute the restore.

Per user feedback in #35566, he change, however, disable users from installing unlisted tools. This feature was added in #36021 if specifying exact match. However, since the exact match refers to input [version]. (referred to NuGet package version reference) come with bracket, this caused surprise for some users using bare version as exact version match.

The intended way to fix this is to allow bare version of .NET tool to interpret as specific version, i.e. version 5.0.0 refers to the exact version match of 5.0.0 instead of [5.0.0, ). To add this feature, a semvar detection is added when getting and parsing the version range in GetVersionRange(). Changes are validated by tests.

Testing
Existing unit tests passed without changes. New tested are added to validate an unlisted bar version tool can be installed with exact version match withtout bracket specified. The new testing scenarios pass with changes in the pull request.

Risk
Low. This change adds a notation that was missed from breaking change without adding complexity to the behavior.

Original description
Per conversation #35566, specifically discussions on comment, this change is made to accept bare versions in .NET tools as NuGet exact version. For example, e.g. --version 1.2.3 would be interpreted by the NuGet package downloader as [1.2.3]

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[JL03-Yue]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[baronfel]

This looks great! I think another team member should take a look, but I'm happy with it :)

[dsplaisted]

Looking into this, I realized that it's possible to specify floating versions, for example --version 1.0.*. Do we have any tests covering that scenario? If not it might be a good idea to add some.