Expose --delay and --max-attempts for wait commands (#1295)

[minjcho]

Issue #, if available:
Fixes #1295

Description of changes:

• Add --delay and --max-attempts arguments to waiter commands.
• Pass the provided values through WaiterConfig when invoking waiter.wait().
• Update waiter help text to document the new options.
• Add unit coverage for argument parsing, help output, and waiter config injection.

Description of tests:

• Added unit tests covering argument parsing, help output, and waiter config injection.
• Ran python -m pytest tests/unit/customizations/test_waiters.py -q — all pass.
• Succeeded manual testing described below.

Manual testing:

Verified the new flags appear in the generated help output:

aws ec2 wait instance-running help

I confirmed that [--delay <value>] and [--max-attempts <value>] are listed in the synopsis and documented in the options section.

Then I ran:

aws ec2 wait instance-running --instance-ids <YOUR_INSTANCE_ID> --delay 5 --max-attempts 10

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[minjcho]

Added input validation for --delay and --max-attempts

Since other CLI params don't check non-positive values at the CLI layer (they rely on botocore's ParamValidator or the AWS server to reject them), I initially didn't add validation here either.

But I found that WaiterConfig is a special case — it's popped from kwargs via kwargs.pop('WaiterConfig', {}) before reaching ParamValidator or the API server, and consumed locally in time.sleep() and a loop counter. No layer validates these values:

• --delay -1 → ValueError: sleep length must be non-negative (Python runtime error from time.sleep(-1))
• --delay 0 → rapid-fire API calls with no sleep interval
• --max-attempts 0 or -1 → polls once, then immediately raises WaiterError

Added validation in WaiterArgument.add_to_params matching the waiter JSON schema constraints (delay >= 0, maxAttempts >= 1 from botocore/tests/functional/test_waiter_config.py):

$ aws ec2 wait instance-running --instance-ids i-123 --delay -1
aws: [ERROR]: --delay must be a non-negative integer, got -1

$ aws ec2 wait instance-running --instance-ids i-123 --max-attempts 0
aws: [ERROR]: --max-attempts must be a positive integer, got 0

Added 7 unit tests covering rejection and acceptance boundaries.

I'll also file a separate issue on botocore for adding the same validation in Waiter.wait(), since boto3 users are equally affected.