Move KDoc to be more discoverable

[twyatt]

KDoc was on the concrete implementations, which from the standpoint of a consumer of the library, you're probably going to be examining the extension functions you call or the interfaces that are returned.

See also: Should Javadoc comments be added to the implementation?

[codecov]

Codecov Report

Merging #55 into develop will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop      #55   +/-   ##
==========================================
  Coverage      74.89%   74.89%           
  Complexity        36       36           
==========================================
  Files             14       14           
  Lines            243      243           
  Branches          26       26           
==========================================
  Hits             182      182           
  Misses            53       53           
  Partials           8        8           

Impacted Files	Coverage Δ	Complexity Δ
core/src/main/java/android/BluetoothDevice.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
core/src/main/java/device/CoroutinesDevice.kt	85.71% <ø> (ø)	3.00 <0.00> (ø)
core/src/main/java/gatt/CoroutinesGatt.kt	47.36% <ø> (ø)	9.00 <0.00> (ø)
core/src/main/java/gatt/Gatt.kt	100.00% <ø> (ø)	0.00 <0.00> (ø)