[v2] Include openssl and ICU statically linked (#8074)

We had to revert the earlier static linking change due to libicu version
incompatibilities:

- original PR: https://github.com/neondatabase/neon/pull/7956
- revert PR: https://github.com/neondatabase/neon/pull/8003

Specifically, the problem manifests for existing projects as error

```
DETAIL:  The collation in the database was created using version 153.120.42, but the operating system provides version 153.14.37.
```

So, this PR reintroduces the original change but with the exact same
libicu version as in Debian `bullseye`, i.e., the libicu version that
we're using today.
This avoids the version incompatibility.


Additional changes made by Christian
====================================
- `hashFiles` can take multiple arguments, use that feature
- validation of the libicu tarball checksum
- parallel build (`-j $(nproc)`) for openssl and libicu

Follow-ups
==========

Debian bullseye has a few patches on top of libicu:
https://sources.debian.org/patches/icu/67.1-7/
We still decide whether we need to include these patches or not.
=> https://github.com/neondatabase/cloud/issues/14527

Eventually, we'll have to figure out an upgrade story for libicu.
That work is tracked in epic
https://github.com/neondatabase/cloud/issues/14525.

The OpenSSL version in this PR is arbitrary.
We should use `1.1.1w` + Debian patches if applicable.
See https://github.com/neondatabase/cloud/issues/14526.

Longer-term:
* https://github.com/neondatabase/cloud/issues/14519
* https://github.com/neondatabase/cloud/issues/14525

Refs
====

Co-authored-by: Christian Schwarz <christian@neon.tech>

refs https://github.com/neondatabase/cloud/issues/12648

---------

Co-authored-by: Rahul Patil <rahul@neon.tech>

Dockerfile

@@ -69,8 +69,6 @@ RUN set -e \
     && apt install -y \
         libreadline-dev \
         libseccomp-dev \
-        libicu67 \
-        openssl \
         ca-certificates \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
     && useradd -d /data neon \