feat/23: add secret command group with get & gen-random sub-commands

[narenaryan]

Description

This PR introduces a new command group called secret with sub-commands get, gen-random.

1. get: Audit a secret from a vault
2. gen-random: Generate a crypto-safe random sequence to use for rotated keys.
3. Improve help texts for all commands
4. Unit tests for new commands

Manual tests

AWS - ✅
Azure - ✅
GCP - ✅

[coveralls]

Pull Request Test Coverage Report for Build 12781546696

Details

• 39 of 72 (54.17%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-5.4%) to 74.528%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/whispr/about.py	0	1	0.0%
src/whispr/cli.py	0	32	0.0%

Totals
Change from base Build 12500360172:	-5.4%
Covered Lines:	237
Relevant Lines:	318

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💛 - Coveralls