Implement new QOL improvements seen on RaanGi's fork

[sasspaper]

RaanGi's fork of PSVShell got some really cool new functionalities. This plugin is naturally superior due to PS1 and PSP support so it would be cool to have these new features in this version.

[GrapheneCt]

I don't think dynamic overclocking is worth the effort on Vita since CPU power draw mainly depends on voltage and not frequency. And there is nothing to overclock on PSP side so adding support for it is pointless.

[sasspaper]

For PSP and PS1 the utility is to underclock and preserve the battery.

[GrapheneCt]

Underclocking for pspemu is not recommended since ARM operates as media engine for psp.