Migrate to pyth network (#727)

* remove direct helium-program-library dep in favor of helium-anchor-gen

* bump to latest anchor gen

* use helium/helium-anchor-gen instead of lthiery/helium-anchor-gen

* Migrate to pyth network

* Use most optimistic price, not the most conservative

* Fix clippy issue

* Add back standard price gen for HST and IOT

* Remove non-taskmanager code from price generator

* Same as prev

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Co-authored-by: lthiery <[email protected]>
Co-authored-by: Andrew McKenzie <[email protected]>