fix(share/availability): add missing protection for autobatch

[walldiss]

Initially reported as panic by @Wondertan

fatal error: concurrent map iteration and map write goroutine 424607 [running]: [github.com/ipfs/go-datastore/autobatch.(*Datastore).Flush(0xc0015ff300](https://github.com/ipfs/go-datastore/autobatch.(*Datastore).Flush(0xc0015ff300), {0x3aacc20, 0xc00bb3b340}) /go/pkg/mod/github.com/ipfs/[email protected]/autobatch/autobatch.go:108 +0xa5 [github.com/ipfs/go-datastore/autobatch.(*Datastore).Put(...)](https://github.com/ipfs/go-datastore/autobatch.(*Datastore).Put(...)) /go/pkg/mod/github.com/ipfs/[email protected]/autobatch/autobatch.go:67 [github.com/celestiaorg/celestia-node/share/availability/light.(*ShareAvailability).SharesAvailable(0xc00050ba40](https://github.com/celestiaorg/celestia-node/share/availability/light.(*ShareAvailability).SharesAvailable(0xc00050ba40), {0x3aacc20, 0xc00bb3b340}, 0xc00694c180) /src/share/availability/light/availability.go:154 +0xab9 [github.com/celestiaorg/celestia-node/das.(*DASer).sample(0xc0014da1a0](https://github.com/celestiaorg/celestia-node/das.(*DASer).sample(0xc0014da1a0), {0x3aacc20, 0xc00bb3b340}, 0xc00694c180) /src/das/daser.go:171 +0xc9 [github.com/celestiaorg/celestia-node/das.(*worker).sample(0xc00bdb6480](https://github.com/celestiaorg/celestia-node/das.(*worker).sample(0xc00bdb6480), {0x3aacbb0, 0xc002286a00}, 0x2540be4000, 0xc00fa7feff?) /src/das/worker.go:121 +0xe2 [github.com/celestiaorg/celestia-node/das.(*worker).run(0xc00bdb6480](https://github.com/celestiaorg/celestia-node/das.(*worker).run(0xc00bdb6480), {0x3aacbb0, 0xc002286a00}, 0x2540be4000, 0xc0018fa3f0) /src/das/worker.go:81 +0x254 [github.com/celestiaorg/celestia-node/das.(*samplingCoordinator).runWorker.func1()](https://github.com/celestiaorg/celestia-node/das.(*samplingCoordinator).runWorker.func1()) /src/das/coordinator.go:112 +0x68 created by [github.com/celestiaorg/celestia-node/das.(*samplingCoordinator).runWorker](https://github.com/celestiaorg/celestia-node/das.(*samplingCoordinator).runWorker) in goroutine 560 /src/das/coordinator.go:110 +0x317

The panic was caused by concurrent access to autobatch datastore due to lack of sync protection on Flush call. This PR adds missing mutex protection for Flush call, as well as Delete, which also had protection missing .

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.51%. Comparing base (2469e7a) to head (c8fb594).
Report is 403 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3988      +/-   ##
==========================================
+ Coverage   44.83%   45.51%   +0.68%     
==========================================
  Files         265      308      +43     
  Lines       14620    21995    +7375     
==========================================
+ Hits         6555    10012    +3457     
- Misses       7313    10912    +3599     
- Partials      752     1071     +319     

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[cristaloleg]

sgtm