Add version incompatibility warning to Connect

[ravicious]

Closes #32555.

TODO:

• Show a warning in FormLogin.
  • We can reuse the copy from tsh.

    teleport/lib/client/api.go

    Lines 4409 to 4436 in 9ca0592

    	case ClientVersionTooOld:
    	return fmt.Sprintf(`
    	WARNING
    	Detected potentially incompatible client and server versions.
    	Minimum client version supported by the server is %v but you are using %v.
    	Please upgrade tsh to %v or newer or use the --skip-version-check flag to bypass this check.
    	Future versions of tsh will fail when incompatible versions are detected.
    	`,
    	versions.MinClient, versions.Client, versions.MinClient), nil
    	case ClientVersionTooNew:
    	serverMajorVersion, err := utils.MajorSemver(versions.Server)
    	if err != nil {
    	return "", trace.Wrap(err)
    	}
    	serverVersionWithWildcards, err := utils.MajorSemverWithWildcards(serverMajorVersion)
    	if err != nil {
    	return "", trace.Wrap(err)
    	}
    	return fmt.Sprintf(`
    	WARNING
    	Detected potentially incompatible client and server versions.
    	Maximum client version supported by the server is %v but you are using %v.
    	Please downgrade tsh to %v or use the --skip-version-check flag to bypass this check.
    	Future versions of tsh will fail when incompatible versions are detected.
    	`,
    	serverVersionWithWildcards, versions.Client, serverVersionWithWildcards), nil

• Add story (stories?).
• Add a config option for skipping version check.
  • I imagine it'd be cool to be able to change the config option straight from the warning itself. If it's too much work, just skip it.
  • In tsh, the flag completely skips the version check. Connect will still perform it, but it should simply not display the warning.