Add `databricks_mws_network_connectivity_config` resource for configuring Serverless network connectivity

[grayluck]

Changes

This change introduces Network Connectivity Config object as an account level object.

Tests

• [x] make test run locally
• [x] relevant change in docs/ folder
• [x] covered with integration tests in internal/acceptance
• [x] relevant acceptance tests are passing
• [x] using Go SDK

Both unit and acceptance tests added.

Manual tests for import:

[codecov-commenter]

Codecov Report

Merging #2671 (0e6e375) into master (205b67c) will decrease coverage by 0.25%. Report is 18 commits behind head on master. The diff coverage is 96.77%.

@@            Coverage Diff             @@
##           master    #2671      +/-   ##
==========================================
- Coverage   84.65%   84.40%   -0.25%     
==========================================
  Files         152      152              
  Lines       13240    13332      +92     
==========================================
+ Hits        11208    11253      +45     
- Misses       1418     1464      +46     
- Partials      614      615       +1     

Files	Coverage Δ
provider/provider.go	94.28% <100.00%> (+0.03%)	:arrow_up:
mws/resource_mws_network_connectivity_config.go	90.69% <90.69%> (ø)

... and 7 files with indirect coverage changes