Readme: Update MariaDB minimum version requirement.

[hellofromTonya]

Ref: ​https://meta.trac.wordpress.org/ticket/6322

Once the minimum version is bumped, then update the version in the readme.html file from 10.2 to 10.3.

Why?

​MariaDB 10.2 is no longer supported as of 23 May 2022, whereas 10.3 is supported until 25 May 2023.

[hellofromTonya]

As this ticket is dependent upon the ​meta ticket, need to temporarily skip the Tests_External_HTTP_Basic::test_readme_mariadb_version() test. Why? The test is checking EOL and fails.

Note: Revert the temporary skip once the version is bumped.

Temporarily skip the MariaDB version test due to 10.2 no longer being supported (EOL) as of 23 May 2022.

Trac ticket: https://core.trac.wordpress.org/ticket/55791

[hellofromTonya]

In 53431:

Build/Test Tools: Temporarily skip MariaDB version test.

TEMPORARY COMMIT.

MariaDB version 10.2 is no longer supported as of 23 May 2022. This commit temporarily skips the version test. Why? To avoid test failures during this period, i.e. until the version is bummped and readme.html file changed.

See #55791, ​Meta5999.

Committed via https://core.trac.wordpress.org/changeset/53431.

[SergeyBiryukov]

In 53433:

Tests: Improve the assertions in recommended MySQL and MariaDB version tests.

Comparing human-readable dates instead of numeric timestamps gives identical results, but makes the message more clear in case of failure.

Follow-up to [33946], [52418], [52421], [52424].

See #55791, #55652.

[SergeyBiryukov]

In 53435:

General: Bump the recommended MariaDB version in readme.html.

MariaDB 10.2 has reached EOL in May 2022. The recommended minimum is bumped to 10.3 for now.

Follow-up to [52319], [52358], [52420], [52424], [53431], [53433], ​[meta11866].

Props hellofromTonya.
Fixes #55791. See ​#meta6322.

[SergeyBiryukov]

In 54069:

Site Health: Bump the recommended MySQL and MariaDB versions.

• MySQL 5.6 has reached EOL (“End of Life”) in February 2021. The recommended minimum is bumped to 5.7 for now.
• MariaDB 10.2 has reached EOL in May 2022. The recommended minimum is bumped to 10.3 for now.

This commit brings the Site Health recommendations in line with readme.html.

Includes:

• Adding two unit tests to ensure the SQL server versions recommended by Site Health match readme.html.
• Consistently declaring the recommended and required versions as the WP_Site_Health class properties.
• Renaming some pre-existing private properties for clarity.

Follow-up to [44986], [52319], [52358], [52420], [52424], [53431], [53433], [53435], ​[meta11407], ​[meta11866].

See #55791, ​#meta5999, ​#meta6322.

[SergeyBiryukov]

In 54076:

Tests: Correct the tests for Site Health SQL versions matching readme.html.

These tests should check the initial $mysql_recommended_version and $mariadb_recommended_version properties, as WP_Site_Health::prepare_sql_data() redefines the former with the latter to simplify further processing if MariaDB is used, leading to a test failure:

Tests_Site_Health::test_mysql_recommended_version_matches_readme_html
Failed asserting that two strings are identical.
--- Expected
+++ Actual
@@ @@
-'5.7'
+'10.3'

This commit uses the initial property values to ensure the correct versions are being compared.

Follow-up to [54069].

See #55791.