Ensure main file has default coverage if required. (#7169)

	* Extract common code for coverage setup.
	---
	 iseq.c | 13 +++++++++++--
	 1 file changed, 11 insertions(+), 2 deletions(-)

	More coverage tests & specs. (#7171)

	* Add spec for eval and line coverage.

	* Add test for main file coverage.
	---
	 spec/ruby/library/coverage/start_spec.rb | 8 +++++++-
	 test/coverage/autostart.rb               | 2 ++
	 test/coverage/main.rb                    | 1 +
	 test/coverage/test_coverage.rb           | 7 +++++++
	 4 files changed, 17 insertions(+), 1 deletion(-)
	 create mode 100644 test/coverage/autostart.rb
	 create mode 100644 test/coverage/main.rb

`throw TAG_BREAK` instruction makes a jump only if the continuation of
catch of TAG_BREAK exactly matches the instruction immediately following
the "send" instruction that is currently being executed. Otherwise, it
seems to determine break from proc-closure.

Branch coverage may insert some recording instructions after "send"
instruction, which broke the conditions for TAG_BREAK to work properly.

This change forces to set the continuation of catch of TAG_BREAK
immediately after "send" (or "invokesuper") instruction.

[Bug #18991]

At that commit, I fixed a wrong conditional expression that was always
true.  However, that seemed to have caused a regression. [Bug #18906]

This change removes the condition to make the code always enabled.
It had been enabled until that commit, albeit unintentionally, and even
if it is enabled it only consumes a tiny bit of memory, so I believe it
is harmless. [Bug #18906]

* Make Coverage suspendable

Add `Coverage.suspend`, `Coverage.resume` and some methods.

[Feature #18176] [ruby-core:105321]

If the type is ADJUST we don't want to treat it like an INSN so we have
to check the type before reading from `insn_info.events`.

[Bug #18001] [ruby-core:104371]

Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>