Use tuples for default arguments in DAP

My co-worker Kévin taught me that using a mutable object as a default
argument in Python is somewhat dangerous, because the object is
created a single time (when the function is defined), and so if it is
mutated in the body of the function, the changes will stick around.

This patch changes the cases like this in DAP to use () rather than []
as the default.  This patch is merely preventative, as no bugs like
this are in the code.

gdb/python/lib/gdb/dap/breakpoint.py

diff --git a/gdb/python/lib/gdb/dap/breakpoint.py b/gdb/python/lib/gdb/dap/breakpoint.py
index 877069f..8ffa182 100644
--- a/gdb/python/lib/gdb/dap/breakpoint.py
+++ b/gdb/python/lib/gdb/dap/breakpoint.py
@@ -96,7 +96,7 @@
 
 
 @request("setBreakpoints")
-def set_breakpoint(*, source, breakpoints=[], **args):
+def set_breakpoint(*, source, breakpoints=(), **args):
     if "path" not in source:
         result = []
     else:
@@ -188,7 +188,7 @@
     "label": "Ada exceptions",
     "supportsCondition": True,
 }))
-def set_exception_breakpoints(*, filters, filterOptions=[], **args):
+def set_exception_breakpoints(*, filters, filterOptions=(), **args):
     # Convert the 'filters' to the filter-options style.
     options = [{"filterId": filter} for filter in filters]
     options.extend(filterOptions)

gdb/python/lib/gdb/dap/launch.py

diff --git a/gdb/python/lib/gdb/dap/launch.py b/gdb/python/lib/gdb/dap/launch.py
index a46be1d..dc4bf3c 100644
--- a/gdb/python/lib/gdb/dap/launch.py
+++ b/gdb/python/lib/gdb/dap/launch.py
@@ -36,7 +36,7 @@
 # from implementations.  Any additions or changes here should be
 # documented in the gdb manual.
 @request("launch")
-def launch(*, program=None, args=[], env=None, **extra):
+def launch(*, program=None, args=(), env=None, **extra):
     if program is not None:
         global _program
         _program = program