Copy share package into Rollkit

[Manav-Aggarwal]

Closes: #887

Copy parts of share package relating to compact shares. We plan to later extract common code into a separate repo that both celestia-app and rollkit can use.

Changes needed to this code for use in rollkit will be handled in a later PR.

Also, extracts parts needed to resolve dependencies, specifically, namespace, appconsts, and `testfactory.

[codecov]

Codecov Report

Patch coverage: 69.28% and project coverage change: +0.92 🎉

Comparison is base (acf0090) 55.17% compared to head (85671ec) 56.09%.

Additional details and impacted files

@@ Coverage Diff @@## main #888 +/- ##
==========================================
+ Coverage 55.17% 56.09% +0.92% 
==========================================
Files 54 66 +12 Lines 9985 10698 +713 ==========================================
+ Hits 5509 6001 +492 - Misses 3656 3829 +173 - Partials 820 868 +48 

Impacted Files	Coverage Δ
libs/namespace/random_namespace.go	0.00% <0.00%> (ø)
libs/namespace/random_blob.go	53.33% <53.33%> (ø)
libs/shares/shares.go	53.90% <53.90%> (ø)
libs/shares/parse_compact_shares.go	64.00% <64.00%> (ø)
libs/shares/split_compact_shares.go	66.66% <66.66%> (ø)
libs/namespace/namespace.go	67.14% <67.14%> (ø)
libs/shares/utils.go	73.91% <73.91%> (ø)
libs/shares/share_builder.go	76.31% <76.31%> (ø)
libs/testfactory/txs.go	88.88% <88.88%> (ø)
libs/shares/share_sequence.go	93.47% <93.47%> (ø)
... and 2 more

... and 2 files with indirect coverage changes

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[nashqueue]

Approve, as this is just a copy-paste from core and will be extracted later.

[tzdybal]

What about putting this new code into a subdirectory? For example libs/shares or just libs/ or something? I think this will make things cleaner and will make planned extraction easier.