This commit changes `deno upgrade` subcommand to accept
a positional argument that can be either a version, release channel
name or a git hash, making invocations of `deno upgrade` much
more concise:
```
# before
$ deno upgrade --version 1.46.0
# after
$ deno upgrade 1.46.0
```
```
# before
$ deno upgrade --canary
# after
$ deno upgrade canary
```
```
# specific canary version before
$ deno upgrade --canary --version f042c39180
# after
$ deno upgrade f042c39180
```
Old flags are still supported, but hidden from the help output.
c94c5cddb1