Fix PHP 7.4 deprecation: array/string curly braces access

[jfcherng]

Deprecated: Array and string offset access syntax with curly braces is deprecated

Hopefully these are all (or most) of them:

[Clover@Clover-NB phpmyadmin](master)$ rg "(\\$|->|::)[A-Za-z0-9_]+\{"
libraries\replication.inc.php:125:// set $server_{master/slave}_status and assign values
libraries\classes\Url.php:253:                $separator = $arg_separator{0};
libraries\classes\Server\Privileges.php:4014:                if ($sql_query{0} != '#') {
libraries\classes\Server\Privileges.php:4269:            if ($sql_query{0} != '#') {

https://github.com/php/php-src/blob/0e6e2297fcb27103cc5d550ee8434680ff1e879e/UPGRADING#L356-L357

---

Also apply to the QA_4_9 branch?

[MauricioFauth]

Also apply to the QA_4_9 branch?

Yes. You can target QA_4_9 and then we merge it to the others branches.

[phpmyadmin-bot]

This pull requests contains too many commits, in most cases it is caused by wrong merge target. In case you have forked master branch you should also ask merging to master branch. See GitHub documentation for more details.

[codecov]

Codecov Report

Merging #15404 into QA_4_9 will decrease coverage by 2.56%.
The diff coverage is 3.82%.

@@             Coverage Diff              @@
##             QA_4_9   #15404      +/-   ##
============================================
- Coverage     55.57%   53.01%   -2.57%     
+ Complexity    14510    14029     -481     
============================================
  Files           494      482      -12     
  Lines         71101    62052    -9049     
============================================
- Hits          39517    32897    -6620     
+ Misses        31584    29155    -2429

[codecov]

Codecov Report

Merging #15404 into QA_4_9 will not change coverage.
The diff coverage is 66.66%.

@@            Coverage Diff            @@
##             QA_4_9   #15404   +/-   ##
=========================================
  Coverage     55.57%   55.57%           
  Complexity    14510    14510           
=========================================
  Files           494      494           
  Lines         71101    71101           
=========================================
  Hits          39517    39517           
  Misses        31584    31584

[jfcherng]

Rebased to QA_4_9.

[MauricioFauth]

Merged, thanks for your contribution!

[ibennetch]

Great, thanks for this!