Backport of Fix panic when setting odr env vars into release/0.10.x

[hc-github-team-waypoint]

Backport

This PR is auto-generated from #3995 to be assessed for backporting due to the inclusion of the label backport/0.10.x.

The below text is copied from the body of the original PR.

---

Prior to this, assignment to the nil map would panic. E.x:

$ waypoint runner profile set -name=k8s -plugin-type=kubernetes -env-var=container=docker
❌ Updating runner profile "k8s" ("01GEMHHFSA3K6XXQR4Q0FVCKGJ")...
panic: assignment to entry in nil map

goroutine 1 [running]:
github.com/hashicorp/waypoint/internal/cli.(*RunnerProfileSetCommand).Run(0xc000246880, {0xc000311940, 0x6, 0xc})
	/Users/izaaklauer/dev/waypoint/internal/cli/runner_profile_set.go:231 +0x15e5
github.com/mitchellh/cli.(*CLI).Run(0xc00056a280)
	/Users/izaaklauer/go/pkg/mod/github.com/mitchellh/cli@v1.1.2/cli.go:262 +0x5f8
github.com/hashicorp/waypoint/internal/cli.Main({0xc000198000?, 0x3813f60?, 0xc0000021a0?})
	/Users/izaaklauer/dev/waypoint/internal/cli/main.go:127 +0x545
main.main()
	/Users/izaaklauer/dev/waypoint/cmd/waypoint/main.go:14 +0x7f