fix(pretty-format): use --pretty in any position

[va-an]

Description

Fix --pretty flag to work in any position by marking it as a global argument.

Previously the flag only worked before subcommands (bdk-cli --pretty key generate) but failed after
(bdk-cli key generate --pretty).

Notes to the reviewers

Before the fix:
Works:

-> % cargo run -- --pretty key generate
+-------------+-----------------------------------------------------------------------------------------------------------------+
| Fingerprint | 3e68be40                                                                                                        |
+-------------+-----------------------------------------------------------------------------------------------------------------+
| Mnemonic    | wheat equip exhaust funny panic lend message champion slim derive alcohol differ                                |
+-------------+-----------------------------------------------------------------------------------------------------------------+
| Xprv        | tprv8ZgxMBicQKsPdmyStjLXkChBJnUa5DBVJY5J46C3qbe98623M9uqD9wrDtcSZe4hLCodZdKacuY8YPzrNWFUEUwSrpa12KiEBikwLTjiYWP |
+-------------+-----------------------------------------------------------------------------------------------------------------+

Doesn't work:

-> % cargo run -- key generate --pretty
error: unexpected argument '--pretty' found

Usage: bdk-cli key generate [OPTIONS]

For more information, try '--help'.

Changelog notice

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[coveralls]

Pull Request Test Coverage Report for Build 18762217126

Details

• 0 of 2 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+5.6%) to 14.43%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/handlers.rs	0	2	0.0%

Totals
Change from base Build 18520893551:	5.6%
Covered Lines:	172
Relevant Lines:	1192

---

💛 - Coveralls

[notmandatory]

ACK c475363

good idea!