Install available updates alongside installation of packages to remove known vulnerabilities from images.
Example for issues in plain alpine:3 image (v3.20):
```sh
$ grype alpine:3
✔ Vulnerability DB [updated]
✔ Loaded image alpine:3
✔ Parsed image sha256:1d34ffeaf190be23d3de5a8de0a436676b758f48f
✔ Cataloged contents dac15f325cac528994a5efe78787cd03bdd796979bda52fd
├── ✔ Packages [14 packages]
├── ✔ File digests [77 files]
├── ✔ File metadata [77 locations]
└── ✔ Executables [17 executables]
✔ Scanned for vulnerabilities [8 vulnerability matches]
├── by severity: 0 critical, 0 high, 6 medium, 0 low, 0 negligible (2 unknown)
└── by status: 8 fixed, 0 not-fixed, 0 ignored
NAME INSTALLED FIXED-IN TYPE VULNERABILITY SEVERITY
busybox 1.36.1-r28 1.36.1-r29 apk CVE-2023-42365 Medium
busybox 1.36.1-r28 1.36.1-r29 apk CVE-2023-42364 Medium
busybox-binsh 1.36.1-r28 1.36.1-r29 apk CVE-2023-42365 Medium
busybox-binsh 1.36.1-r28 1.36.1-r29 apk CVE-2023-42364 Medium
libcrypto3 3.3.0-r2 3.3.0-r3 apk CVE-2024-4741 Unknown
libssl3 3.3.0-r2 3.3.0-r3 apk CVE-2024-4741 Unknown
ssl_client 1.36.1-r28 1.36.1-r29 apk CVE-2023-42365 Medium
ssl_client 1.36.1-r28 1.36.1-r29 apk CVE-2023-42364 Medium
```
Issue would be solved by also upgrading installed packages:
```sh
$ apk -U upgrade --no-cache
fetch https://dl-cdn.alpinelinux.org/alpine/v3.20/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.20/community/x86_64/APKINDEX.tar.gz
(1/5) Upgrading busybox (1.36.1-r28 -> 1.36.1-r29)
Executing busybox-1.36.1-r29.post-upgrade
(2/5) Upgrading busybox-binsh (1.36.1-r28 -> 1.36.1-r29)
(3/5) Upgrading libcrypto3 (3.3.0-r2 -> 3.3.1-r0)
(4/5) Upgrading libssl3 (3.3.0-r2 -> 3.3.1-r0)
(5/5) Upgrading ssl_client (1.36.1-r28 -> 1.36.1-r29)
Executing busybox-1.36.1-r29.trigger
OK: 8 MiB in 14 packages
```
Furthermore, this commit reduces accidental complexity from the Docker build process.
Most notably, use pre-made official golang images for building postgres-operator.