some cleanups and rename on start type

[hzxuzhonghu]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #

Special notes for you're reviewer:

Does this PR introduce a user-facing change?:

[YaoZengzeng]

Add comments about when to use kmeshExitType and when to use kmeshStartType, it is also very confusing that they are both of type StartType, maybe we need better naming.

[hzxuzhonghu]

kmeshStartType is used during bootsttap

kmeshExitType is used during exit, to indicate whether keep bpf prog/maps or not

Previously one var is used to indicate both, confusing to me

[YaoZengzeng]

Suggested change

	assert.Equal(t, Restart, GetExitType(), "set kmesh close status:Restart failed")
	assert.Equal(t, Restart, GetExitType(), "set kmesh exit type to Restart failed")

[codecov]

Codecov Report

Attention: Patch coverage is 70.83333% with 7 lines in your changes missing coverage. Please review.

Project coverage is 52.88%. Comparing base (e3762f2) to head (daf352a).
Report is 79 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/bpf/bpf.go	75.00%	3 Missing and 1 partial ⚠️
pkg/bpf/bpf_restart.go	62.50%	2 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
pkg/bpf/bpf_restart.go	62.50% <62.50%> (-2.62%)	⬇️
pkg/bpf/bpf.go	41.81% <75.00%> (ø)

... and 14 files with indirect coverage changes

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[supercharge-xsy]

/lgtm
/approve

[kmesh-bot]

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