Generic/UpperCaseConstantName: false positives for namespaced function called define()

[jrfnl]

Describe the bug

Inspired by #665

When a codebase contains a namespaced function called define, the sniff may throw false positives.

Code sample

File 1:

namespace Foo;

function define($name, $value) {
    // Do something.
}

// These are calls to the namespaced function, not the global one.
define('name', 'value');
namespace\define('name', 'value');

// This is a call to another namespaced function `Foo\Sub\define()`, not the global one.
Sub\define('name', 'value');

// This is a call to yet another namespaced function `My\Other\NS\define()`, not the global one.
\My\Other\NS\define('name', 'value');

File 2:

namespace Foo;

use function Bar\define;

// This is a call to the imported namespaced function, not the global one.
define('name', 'value');

To reproduce

Steps to reproduce the behavior:

1. Create a file called test.php with the code sample above...
2. Run phpcs test.php --standard=generic --sniffs=generic.namingconventions.uppercaseconstantname
3. See error message displayed

# File 1:
---------------------------------------------------------------------------------------------------------------------------------------------------
FOUND 4 ERRORS AFFECTING 4 LINES
---------------------------------------------------------------------------------------------------------------------------------------------------
 10 | ERROR | Constants must be uppercase; expected 'NAME' but found 'name' (Generic.NamingConventions.UpperCaseConstantName.ConstantNotUpperCase)
 11 | ERROR | Constants must be uppercase; expected 'NAME' but found 'name' (Generic.NamingConventions.UpperCaseConstantName.ConstantNotUpperCase)
 14 | ERROR | Constants must be uppercase; expected 'NAME' but found 'name' (Generic.NamingConventions.UpperCaseConstantName.ConstantNotUpperCase)
 17 | ERROR | Constants must be uppercase; expected 'NAME' but found 'name' (Generic.NamingConventions.UpperCaseConstantName.ConstantNotUpperCase)
---------------------------------------------------------------------------------------------------------------------------------------------------

# File 2:
--------------------------------------------------------------------------------------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
--------------------------------------------------------------------------------------------------------------------------------------------------
 8 | ERROR | Constants must be uppercase; expected 'NAME' but found 'name' (Generic.NamingConventions.UpperCaseConstantName.ConstantNotUpperCase)
--------------------------------------------------------------------------------------------------------------------------------------------------

Expected behavior

No errors.

Versions (please complete the following information)

Operating System	not relevant
PHP version	not relevant
PHP_CodeSniffer version	master
Standard	Generic
Install type	not relevant

Additional context

Add any other context about the problem here.

Please confirm

• I have searched the issue list and am not opening a duplicate issue.
• I have read the Contribution Guidelines and this is not a support question.
• I confirm that this bug is a bug in PHP_CodeSniffer and not in one of the external standards.
• I have verified the issue still exists in the master branch of PHP_CodeSniffer.