Session.get_common: Fix the return values for options B/J/U/g/n/p/s and improve option checking

[seisman]

Session.get_common checks if an option is set and returns its value if possible.

As shown below, it has bugs for some options. For examples, when -fg/-fig is used, it returns True, while -fog returns 1.

In [1]: from pygmt.clib import Session

In [2]: with Session() as lib:
   ...:     lib.call_module("basemap", ["-R0/10/0/10", "-JX10c", "-Baf", "-fg"])
   ...:     print(lib.get_common("f"))
   ...:
True

In [3]: with Session() as lib:
   ...:     lib.call_module("basemap", ["-R0/10/0/10", "-JX10c", "-Baf", "-fig"])
   ...:     print(lib.get_common("f"))
   ...:
True

In [4]: with Session() as lib:
   ...:     lib.call_module("basemap", ["-R0/10/0/10", "-JX10c", "-Baf", "-fog"])
   ...:     print(lib.get_common("f"))
   ...:
1

This PR fixes the bug. With the changes in this PR, it returns 0 or 1 when set, and False when not set.

Bugs detected and fixed by Claude, reviewed by @seisman