[8.13](backport #37720) [Metricbeat][Postgresql][Database] Fix fields not being parsed correctly

[mergify]

• Bug

What does this PR do?

Fix postgresql.database.blocks.time.read.ms and postgresql.database.blocks.time.write.ms being captured and reported as a long instead of double thus not being reported at all.

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Closes [Metricbeat] [PostgreSQL] module [database] metricset - wrong mapping for blk_read_time and blk_write_time #25301

---

This is an automatic backport of pull request #37720 done by [Mergify](https://mergify.com).

[elasticmachine]

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