✨ Cli interface to list connected devices

[muchzill4]

Description

Presentation layer for our devices listing.

• Uses tabulate to format output - this can probably be extracted to mbed-tools-lib once we use it in more than one place

Test Coverage

• This change is covered by existing or additional automated tests.
• Manual testing has been performed (and evidence provided) as automated testing was not feasible.
• Additional tests are not required for this change (e.g. documentation update).

[codecov]

Codecov Report

Merging #15 into master will increase coverage by 4.73%.
The diff coverage is 95.23%.

@@            Coverage Diff             @@
##           master      #15      +/-   ##
==========================================
+ Coverage   86.46%   91.19%   +4.73%     
==========================================
  Files          14       15       +1     
  Lines         266      284      +18     
==========================================
+ Hits          230      259      +29     
+ Misses         36       25      -11

Impacted Files	Coverage Δ
mbed_devices/device.py	100% <100%> (+100%)	⬆️
mbed_devices/mbed_tools/cli.py	100% <100%> (ø)
mbed_devices/mbed_devices.py	75% <75%> (+75%)	⬆️