Feature: universal customized parameterization on exchange-correlation functionals

[kirk0830]

Linked Issue

Fix #6269

What's changed?

• Support the customized parameterization on exchange-correlation functionals by introducing two new parameters xc_exch_ext and xc_corr_ext
• Refactor the libxc interface to improve the code matainability

What can do next

• the two newly-introduced parameter xc_exch_ext and xc_corr_ext fasciliate the advanced tuning on xc functionals, although they partially override the as-estabilished parameterization mechansim of exx. However, the parameters of xc should be more systematically organized in a more general way, rather than:

// other codes
		// short-range of B88_X?
		{XC_GGA_X_ITYH, {PARAM.inp.exx_hse_omega}},
		// short-range of LYP_C?
		{XC_GGA_C_LYPR, {0.04918, 0.132, 0.2533, 0.349, 
						 0.35/2.29, 2.0/2.29, PARAM.inp.exx_hse_omega}},
// other codes

[kirk0830]

I have added assertion on the size of parameters list to avoid possible illegal memory access undefined behavior, thanks for information from @jeanwsr~