add more specificity to project-level eligibility

[tvanepps]

This PR adds two notes to make project-level eligibility more explicit:

• strictly necessary software for ethereum to come to consensus
• clients must be able to produce blocks locally to be considered

Members can see the original discussion and notes from the April 1st internal ops call - see this internal discord message for summary and notes

zkEVM/zkVM formal verification eligibility: Trent shared a proposed update to PGs eligibility framework, see the above link for the updated wording. 

• The goal is to make PG eligibility as explicit as possible, by anchoring on "strictly necessary and existential software required to produce blocks and advance the chain"
• MEV boost and light clients are highlighted as two projects that are not eligible (we have been approached by a couple light clients about inclusion in the past)
• Changes to the word were also made to ensure that we set a high bar for new clients, including that their releases are "production-grade" (not pre-releases) and that the client can construct full blocks. 
• Note that the proposed wording could be interpreted to exclude Portal clients (though Portal is not referenced), but this proposed change is not meant to make a decision on that, Portal clients would remain grandfathered into PG as part of this change.
• This change is the first step in overhauling PGs eligibility to account for beam chain / snarkification thats on the horizon. - The beam chain would heavily use zkVMs and zkEVMs, which may or may not be in-protocol, and thus we need to make a decision on if / how to include those in PGs eligibility framework. Ideally this discussion should start "in the coming weeks".