Investigate if we can replace SourceLink translation with git `insteadOf` configuration option

Today we use regex based mapping to translate URLs from internal mirrors to public github repos.

**Proposal**

In the pipeline definition of an official build of a mirrored repository run `git config` command that adds a repo-local configuration option [insteadOf](https://git-scm.com/docs/git-config#Documentation/git-config.txt-urlltbasegtinsteadOf) that replaces a prefix (or multiple prefixes) of internal URL with corresponding prefix of github URL (`https://dnceng@dev.azure.com/dnceng/internal/_git/dotnet-` to `https://github.com/dotnet/`,
`https://dnceng@dev.azure.com/dnceng/internal/_git/Microsoft-` to `https://github.com/Microsoft/`, etc.).

SourceLink applies this configuration switch to remote URLs.