Deepcompile: Make size of activation to free configurable (#7582)
In deepcompile free-activation mode, only activations larger than a
threshold are eagerly freed. The threshold is hardcoded today and thus
may not be suitable in all cases.
This PR first generalizes the dc.init() interface to take the whole
compile_config object, and then converts the threshold into a config
item.
This corresponds to issue 3 of #7577.
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Signed-off-by: Junjie Mao <junjie.mao@linux.alibaba.com>