Add validation for WaiterConfig Delay and MaxAttempts values (#3674)

[minjcho]

Issue #, if available:
Fixes #3674

Description of changes:

Waiter.wait() now validates Delay and MaxAttempts in WaiterConfig
before entering the polling loop.

Previously, invalid values caused confusing Python runtime errors or
silently broken behavior:

• Delay: -1 -> ValueError from time.sleep()
• MaxAttempts: 'abc' -> TypeError from >= comparison
• Delay: 0 -> rapid-fire API calls with no sleep
• MaxAttempts: 0 -> polls once, then immediately raises WaiterError

Invalid values now raise WaiterConfigError with a clear message before
any API call is made. This is consistent with existing waiter config
validation (unsupported version, unknown matcher).

Validation rules:

• Delay: non-negative number (int or float, not bool)
• MaxAttempts: positive integer (>= 1, not bool or float)

Note: this intentionally validates against Python built-in numeric types
only (int, float), consistent with botocore's existing isinstance-based
validation patterns. Third-party numeric types (e.g. numpy.int64) that
previously worked implicitly via duck typing will now need to be converted
to native Python types before being passed in WaiterConfig.

Description of tests:

Added 11 unit tests in tests/unit/test_waiters.py:

Rejection cases (9):

• Delay: -1 (negative)
• Delay: 'fast' (non-numeric)
• Delay: None
• Delay: True (bool)
• MaxAttempts: 0 (zero)
• MaxAttempts: -1 (negative)
• MaxAttempts: 'abc' (non-integer)
• MaxAttempts: True (bool)
• MaxAttempts: 1.5 (float)

Acceptance cases (2):

• Delay: 0, MaxAttempts: 1 (minimum valid)
• Delay: 0.5, MaxAttempts: 1 (float delay)

All rejection tests verify operation_method.assert_not_called() to confirm
no API call is made before validation fails.

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