Update server vendoring

Once we merge most of TOOLS-2022, the server's tools vendoring will likely be broken. Here are the steps required to fix it:

• Relocate vended code to a GOPATH like structure (e.g. src/mongo/gotools/src/github.com/mongodb/mongo-tools and fix "go build" output binary path in Evergreen configs (evergreen.yml and system_perf.yml)
• Update kernel-tools vendoring code to vendor tools to the new directory
• Revendor new tools code
• Update server Evergreen configs (evergreen.yml and system_perf.yml):
  • Remove version string munging shell code
  • Source the new set_goenv.sh file instead of set_gopath.sh and call its functions to set the environment and an ldflags variable
  • Remove gorootvars from functions and buildvariants and add the {{ldflags} argument to all "go build" calls
• Test and backport