v7 release branch does't build

[gilescope]

While the 9.16 branch builds the v7 does not. ( https://github.com/paritytech/cumulus/runs/5006506401?check_suite_focus=true )

I think we can get past the first build failure by a change like

fn host_storage_root() -> Vec<u8> {
	vec[]
	with_externalities(|ext| ext.storage_root(StateVersion::V0))
}

in pallets/parachain-system/src/validate_block/implementation.rs

reverting b03e8bcf151bbf4c20a7d7faa782366fc3554d58 should fix this.

but then there seem to be some clap issues also:

error[E0277]: the trait bound `sc_cli::RunCmd: FromArgMatches` is not satisfied
   --> client/cli/src/lib.rs:126:9
    |
126 |     #[clap(flatten)]
    |            ^^^^^^^ the trait `FromArgMatches` is not implemented for `sc_cli::RunCmd`

(maybe the latest cut has brought in a new version of clap?)

UPDATE:
reverting
b03e8bcf151bbf4c20a7d7faa782366fc3554d58 ,
9c977d6
and fd14576 should fix the build. The latter two are reverted already in the cumulus 9.16 release branch, but not the first one - let me check if something was brought in to fix that.

I also think we need to include: 86f76c5 (as this was on the release branch of cumulus)

[gilescope]

dep of #937

[gilescope]

ah looks like master has gone from structopt to clap.

[gilescope]

reverting #895 sorts out the clap issues. (I presume it is a companion to something that is not in 9.16 though need to confirm that) - I think we can cherry pick 5d7f6a9 to do this.

[gilescope]

also if we cherry pick this commit: ec07b4e to revert #901 then we get something that builds again. Yay.

[gilescope]

Fixed.