Make COPY_EXECUTION_REQUIREMENTS optional

[sluongng]

Currently, we have

bazel-skylib/rules/private/copy_common.bzl

Lines 18 to 45 in fa66e6b

	COPY_EXECUTION_REQUIREMENTS = {
	# ----------------+-----------------------------------------------------------------------------
	# no-remote | Prevents the action or test from being executed remotely or cached remotely.
	# | This is equivalent to using both `no-remote-cache` and `no-remote-exec`.
	# ----------------+-----------------------------------------------------------------------------
	# no-cache | Results in the action or test never being cached (remotely or locally)
	# ----------------+-----------------------------------------------------------------------------
	# See https://bazel.build/reference/be/common-definitions#common-attributes
	#
	# Copying file & directories is entirely IO-bound and there is no point doing this work
	# remotely.
	#
	# Also, remote-execution does not allow source directory inputs, see
	# https://github.com/bazelbuild/bazel/commit/c64421bc35214f0414e4f4226cc953e8c55fa0d2 So we must
	# not attempt to execute remotely in that case.
	#
	# There is also no point pulling the output file or directory from the remote cache since the
	# bytes to copy are already available locally. Conversely, no point in writing to the cache if
	# no one has any reason to check it for this action.
	#
	# Read and writing to disk cache is disabled as well primarily to reduce disk usage on the local
	# machine. A disk cache hit of a directory copy could be slghtly faster than a copy since the
	# disk cache stores the directory artifact as a single entry, but the slight performance bump
	# comes at the cost of heavy disk cache usage, which is an unmanaged directory that grow beyond
	# the bounds of the physical disk.
	"no-remote": "1",
	"no-cache": "1",
	}

which disable remote cache, remote execution, and cache for the Copy* actions.

This is a sane default for a local build, but for a fully remote build with Build without the Bytes turned on, this requirement causes Bazel to fetch the inputs locally, run the action, and upload the outputs. As a result, the build is dramatically slowed down compared to running these actions remotely and letting the RBE system handle the optimization.

I think it would make more sense if we create a separate execution group for these copy actions. The downstream rules/users could decide the default value of these execution properties for the copy group, or to override them.

https://bazel.build/extending/exec-groups

[tetromino]

CC-ing @katre for platform expertise

[katre]

I think this makes sense, where are these used from? Are they parts of other rules? Can we implement this more cleanly with subrules?