Disable tests by default if tools are not found

[mkindahl]

If tools like pg_regress or pg_isolation_regress are not found, an
error is generated telling you that you need to disable the tests
explicitly using REGRESS_CHECKS. This is an inconvenience for the
user since in most cases you just want to build the system with what
you have.

This commit changes that by automatically disabling regression tests,
isolation tests, TAP tests, and formatting targets when tools cannot be
found, which means that users do not normally have to disable tests
explicitly. A notice is still printed that the targets are not added.

In addition, the commit adds an option REQUIRE_ALL_TESTS for the rare
case when you want to make sure that all tests are indeed executed (for
example, in CI runs), which by default is off.

[codecov]

Codecov Report

Merging #3468 (b14ebbc) into master (e1c5a98) will decrease coverage by 55.81%.
The diff coverage is n/a.

❗ Current head b14ebbc differs from pull request most recent head d5a09de. Consider uploading reports for the commit d5a09de to get more accurate results

@@             Coverage Diff             @@
##           master    #3468       +/-   ##
===========================================
- Coverage   90.73%   34.92%   -55.82%     
===========================================
  Files         212      212               
  Lines       36258    36258               
===========================================
- Hits        32900    12664    -20236     
- Misses       3358    23594    +20236     

Impacted Files	Coverage Δ
src/compat.h	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/telemetry.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/remote/utils.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/compression/utils.h	0.00% <0.00%> (-100.00%)	⬇️
tsl/test/src/remote/async.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/nodes/gapfill/locf.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/remote/txn_resolve.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/test/src/remote/txn_id.c	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/remote/data_fetcher.h	0.00% <0.00%> (-100.00%)	⬇️
tsl/src/nodes/gapfill/gapfill.c	0.00% <0.00%> (-100.00%)	⬇️
... and 166 more

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[svenklemm]

make format is entirely optional for the build process. not sure why we would need an option to enable it since it's sufficient and much more user friendly to check at execution time for the availabilty. this is also much more friendly to packagers.

[mkindahl]

make format is entirely optional for the build process. not sure why we would need an option to enable it since it's sufficient and much more user friendly to check at execution time for the availabilty. this is also much more friendly to packagers.

If clang-format does not exist, a build rule to run clang-format using Docker is created instead. We could check for availability of Docker as well and just ignore the situation if docker is not available either, which would indeed be more user-friendly.

However, that raises the issue why we do not do the same when pg_regress is not found. In this case, we generate an error and it needs to be explicitly disabled. If user-friendliness is a goal, then we should disable regress tests when pg_regress is not found instead of erroring out. (And the same reasoning applies to pg_isolation_regress, and TAP tests.)

[mkindahl]

The pull request is updated to by default disable tests if they are not found. It also moves some of the checks for programs to the topmost CMakeLists.txt.