[feat] Allow "LicenseDir" field for non-enterprise usage

[james0209]

What

High-level overview

Introduces LicenseDir field into the following:

• build.GitRevision
• checkpoint.LatestVersion
• releases.ExactVersion
• releases.LatestVersion
• versions.InstallationOptions

Removes LicenseDir field from:

• EnterpriseOptions

build.GitRevision

• When copying the license file (with or without .txt) from the repo, keep the name as-is.
  • Currently, the license file created is always "LICENSE.txt".
• Add destination path for the copied license file to pathsToRemove to match other uses.

checkpoint.LatestVersion

• Pass LicenseDir to DownloadAndUnpack call
• Currently an empty string is passed as checkpoint doesn't support Enterprise, and before this PR, it was assumed that only Enterprise versions would contain a License.

versions.InstallationOptions

• Add LicenseDir to InstallationOptions - same struct that contains InstallDir.

Why

Closes #213

[radeksimko]

This is looking pretty good aside from my inline comments!

Also thanks for handling the situation with enterprise versions. I did not realise we would have when writing the linked issue.

This does imply breaking change but it seems worth making, we just need to call it out in the Changelog (which I can do once it's merged).

[radeksimko]

Mostly minor concerns remaining as per my comments inline. Once those are addressed I'm more than happy to merge this.