Add Azure SQL resources, tests, and samples

[matthchr]

Closes #2318

This cannot be merged until the corresponding Swagger changes are also merged: See Azure/azure-rest-api-specs#22292

If applicable:

• this PR contains documentation
• this PR contains tests

[matthchr]

/ok-to-test sha=37abf95

[matthchr]

/ok-to-test sha=37abf95

[codecov-commenter]

Codecov Report

Merging #2698 (5e2d2bf) into main (0b30147) will decrease coverage by 0.04%.
The diff coverage is 47.42%.

@@            Coverage Diff             @@
##             main    #2698      +/-   ##
==========================================
- Coverage   52.57%   52.53%   -0.04%     
==========================================
  Files         987     1076      +89     
  Lines      377700   390520   +12820     
==========================================
+ Hits       198574   205178    +6604     
- Misses     147682   153085    +5403     
- Partials    31444    32257     +813     

Impacted Files	Coverage Δ
...ervice/v1beta20210501/managed_cluster_types_gen.go	47.70% <ø> (ø)
...a20210501/managed_clusters_agent_pool_types_gen.go	46.59% <ø> (ø)
...v1beta20210501storage/managed_cluster_types_gen.go	55.17% <ø> (ø)
...01storage/managed_clusters_agent_pool_types_gen.go	55.81% <ø> (ø)
...rmysql/v1beta20210501/flexible_server_types_gen.go	52.65% <ø> (ø)
...eta20210501/flexible_servers_database_types_gen.go	48.60% <ø> (ø)
...210501/flexible_servers_firewall_rule_types_gen.go	55.61% <ø> (ø)
...v1beta20210501storage/flexible_server_types_gen.go	55.17% <ø> (ø)
...0501storage/flexible_servers_database_types_gen.go	55.17% <ø> (ø)
...torage/flexible_servers_firewall_rule_types_gen.go	55.17% <ø> (ø)
... and 94 more

... and 6 files with indirect coverage changes

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