Implement signal blocking in integration functions

[cxzhong]

Added signal blocking and unblocking around Python function calls to prevent conflicts with signal handling in external libraries.
Also fix some compiler warnings.
Improve #40980 , Fix #30379

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[cxzhong]

sage: f = lambda x, y: float(gamma_inc(2, 11/5)) * float(sin(x*y)) * float(exp(-x-y))
sage: result = monte_carlo_integral(f, [0, 0], [10, 10], 10000000, algorithm='vegas')
^C---------------------------------------------------------------------------
KeyboardInterrupt                         Traceback (most recent call last)
Cell In[4], line 1
----> 1 result = monte_carlo_integral(f, [Integer(0), Integer(0)], [Integer(10), Integer(10)], Integer(10000000), algorithm='vegas')

File sage/calculus/integration.pyx:724, in sage.calculus.integration.monte_carlo_integral()

KeyboardInterrupt: 

KeyboardInterrupt is normal, it deals with Ctrl+C by itself