[pgAdmin4][Patch#2897] Add support for keyboard navigation in Debugger

Hi,

PFA patch to add keyboard navigation in Debugger module via
Tab/Shift-Tab key.
RM#2897

Also fixed the issue where user was not able to update values in variable's
panel while debugging.
RM#2981

Currrently we have execution related shortcuts using accesskey,
Shortcuts (Execution related)
----------------------------------
<accesskey> + i = Step in
<accesskey> + o = Step over
<accesskey> + c = Continue/Restart
<accesskey> + t = Toggle breakpoint
<accesskey> + x = Clear all breakpoints
<accesskey> + s = Stop

Shortcuts (Panel navigation related)
----------------------------------
Alt + Shift + Right Arrow
Alt + Shift + Left Arrow

Edit/Enter values in Grid (Parameter & Local variables panel's)
-------------------------------------------------------------
Alt + Shift + g

Please review.

*Note:* As of now inner panel's are not getting focused on Tab/Shift-Tab
keys but once RM#2895 <https://redmine.postgresql.org/issues/2895> patch
gets committed it will start working automatically as it's inherited code
which will add tabindex tag automatically on each newly created wcDocker
panel.

--
Regards,
Murtuza Zabuawala
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company