mysql: change default auth plugin from mysql_native_password

[jorgsowa]

Description

Extracted from: #18555

Change mysql_native_password as default auth protocol from codebase:

php-src/ext/mysqlnd/mysqlnd_enum_n_def.h

Line 37 in 7e956f8

#define MYSQLND_DEFAULT_AUTH_PROTOCOL "mysql_native_password"

Plugin mysql_native_password is deprecated in Mysql 8.4 and removed in Mysql 9.0:
https://dev.mysql.com/doc/refman/8.4/en/native-pluggable-authentication.html

[NattyNarwhal]

Note caching_sha2_password in mysqlnd is gated behind if SSL is available; usually on in most builds, but not necessarily in a minimal one (since it uses OpenSSL on unix). We'll have to account for that or mandate it, I assume.