Bump version and update changelog

Use kcov from official Ubuntu 20.04 repository (spack#25385)

* Ubuntu 20.04 provides kcov, so don't build from source

* Use two undocumented options for kcov v3.8

Pipelines: pass relative artifact paths to child jobs (spack#24085)

Passing absolute paths from pipeline generate job to downstream rebuild jobs
causes problems when the CI_PROJECT_DIR is not the same for the generate and
rebuild jobs.  This has happened, for example, when gitlab checks out the
project into a runner-specific directory and different runners are chosen
for the generate and rebuild jobs.

Update CHANGELOG and release version for v0.16.2

upcxx: Install the example files (spack#23832)

This installs the example source files into $prefix/example, for use by the E4S Testsuite and other end users.

Also fixes a harmless copy/paste error.

Compilers: make oneapi ifx version_regex tolerant to wrappers (spack#…

…21742)

If a user creates a wrapper for the ifx binary called ifx_orig,
this causes the ifx --version command to produce:

$ ifx --version
ifx_orig (IFORT) 2021.1 Beta 20201113
Copyright (C) 1985-2020 Intel Corporation. All rights reserved.

The regex for ifx currently expects the output to begin with
"ifx (IFORT)..." so the wrapper would not be detected as ifx. This
PR removes the need for the static "ifx" string which allows wrappers
to be detected as ifx.

In general, the Intel compiler regexes do not include the invoked
executable name (i.e., ifort, icc, icx, etc.), so this is not
expected to cause any issues.

Update CHANGELOG and release version

update CHANGELOG.md for v0.16.0

update CHANGELOG.md for 0.15.4

Merge tag 'v0.15.3' into features/shared