Use EVG distro system uv binaries

[eramongodb]

Similar to mongodb/mongo-cxx-driver#1464, this PR removes the uv-installer.sh script (and related utilities) in favor of using EVG system-provided uv binaries. Distros which are missing a uv binary (rhel84 and debian11) are either disabled (due to plenty of equivalent coverage elsewhere) or use the simple workaround of installing uv into a temporary prefix via the system python binary:

prefix="$(mktemp -d)"
python3 -m pip install --prefix "$prefix" uv
PATH="$prefix/bin:$PATH"

As in mongodb/mongo-cxx-driver#1464, this PR also migrates away from deprecated/EOL/discouraged distros, which include:

• archlinux: no longer actively maintained by DevProd. Since we already have Earthly coverage, the "clang 3.7 (Archlinux)" legacy build variant is removed, as all its tasks have plenty of equivalent coverage by other build variants.
• ubuntu2004: relevant tasks are updated to use ubuntu2204, ubuntu2404, or a RHEL distro instead. This does not include the aws-ubuntu2004 distro (unclear how to migrate).

Notable changes also include:

• Migrating the loadbalanced tasks to Ubuntu 24.04 revealed the lack of a system-provided haproxy binary. The haproxy binary is installed via uv tool as a workaround using the haproxy-cli PyPI package.
• Suppressing memory leak reports by auth+asan tasks due to the libkrb5.so.3 and libgssapi_krb5.so.2 libraries on Ubuntu distros. They seem to be unrelated to our implementation. However, I could not find relevant issues or references.
• Some desperate attempts to address various code coverage warnings and errors which seem to indicate mismatch between source files and executables. I could not fully determine what is really causing these issues.