RUSTSEC-2021-0139: ansi_term is Unmaintained

[github-actions]

ansi_term is Unmaintained

Details
Status	unmaintained
Package	ansi_term
Version	0.12.1
URL	ogham/rust-ansi-term#72
Date	2021-08-18

The maintainer has adviced this crate is deprecated and will not
receive any maintenance.

The crate does not seem to have much dependencies and may or may not be ok to use as-is.

Last release seems to have been three years ago.

Possible Alternative(s)

The below list has not been vetted in any way and may or may not contain alternatives;

• anstyle
• nu-ansi-term
• yansi

See advisory page for additional details.

[rajarshimaitra]

This is causing from clap of structopt..

$ cargo tree -i ansi_term
ansi_term v0.12.1
└── clap v2.34.0
    └── structopt v0.3.26
        └── bdk-cli v0.5.0 

structopt doesn't support clap 3.** .. So we need to wait on them to fix this..

[notmandatory]

I think clap as of 3.x now includes structopt like features. See: https://docs.rs/clap/latest/clap/

So rather than updating structopt we should just switch to clap 3.x, then we should be able to close this issue.

[rajarshimaitra]

Sounds good idea.. Thats what I think we should do.. Shall we just close this one, and create as an enhancement issue?? Would be easier to find for anyone who might be interested taking it up, till I get to it..