Organize rust bindings dependency pins into single issue

[Sam Clark]

Problem:

Every time we pin a dependency in the rust bindings we create a new issue to track when it should be unpinned. This makes it hard to discover which dependencies can be unpinned according when the MSRV is bumped.

Solution:

We could instead have one issue tracking all of the dependency pinning, which sorts each dependency by the required MSRV, as suggested by @jmayclin: #4519 (comment)

[Sam Clark]

for example: aws/s2n-quic#2117

[Sam Clark]

The s2n-quic strategy will be used, where unpin issues are created for each MSRV update that breaks a dependency, and all of the dependencies pinned due to that MSRV will be listed in the issue.