Add attribute hot judgement for INLINE_HINT_known_hot hint.

We set up INLINE_HINT_known_hot hint only when we have profile feedback,
now add function attribute judgement for it, when both caller and callee
have __attribute__((hot)), we will also set up INLINE_HINT_known_hot hint
for it.

With this patch applied,
ADL Multi-copy:    538.imagic_r  16.7%
ICX Multi-copy:    538.imagic_r  15.2%
CLX Multi-copy:    538.imagic_r  12.7%
Znver3 Multi-copy: 538.imagic_r  10.6%
Arm Multi-copy:    538.imagic_r  13.4%

gcc/ChangeLog

	* ipa-inline-analysis.cc (do_estimate_edge_time): Add function attribute
	judgement for INLINE_HINT_known_hot hint.

gcc/testsuite/ChangeLog:

	* gcc.dg/ipa/inlinehint-6.c: New test.