pgsql: ci: Use windows VMs instead of windows containers

ci: Use windows VMs instead of windows containers

So far we have used containers for testing windows on cirrus-ci. Unfortunately
they come with substantial overhead: First, the container images are pulled
onto the host on-demand. Due to the large size of windows containers, that
ends up taking nearly 4 minutes. Secondly, IO is slow, leading to CI runs
taking long.

Thus switch to windows VMs, improving windows CI times by well over 2x.

Author: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Discussion: https://postgr.es/m/211afb88-6df6-b74d-f1b7-84b5f21ad875@gmail.com
Backpatch: 15-, where CI was added

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/98811323c8e9a1995b828a47504b6608f0f3f59a

Modified Files
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.cirrus.yml | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)