checkpatch: add verbose mode

checkpatch: add verbose mode

Add a new verbose mode to checkpatch.pl to emit additional verbose
test descriptions. The verbose mode is optional and can be enabled
by the flag -v or --verbose.

The test descriptions are parsed from the checkpatch documentation
file at `Documentation/dev-tools/checkpatch.rst`. The test
descriptions in the docs are kept in a fixed format grouped by
usage. Some examples of this format are:

  **LINE_SPACING**
    Vertical space is wasted given the limited number of lines an
    editor window can display when multiple blank lines are used.

  **MISSING_SIGN_OFF**
    The patch is missing a Signed-off-by line.  A signed-off-by
    line should be added according to Developer's certificate of
    Origin.

To avoid lengthy output, the verbose description is printed only
for the first instance of a particular message type.

The --verbose option cannot be used along with the --terse option.

Verbose mode can be used with the --list-types option.
The --list-types output also supports color coding now.

Signed-off-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
Link: https://lore.kernel.org/r/20210226093827.12700-3-dwaipayanray1@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>