Assign service type labels to database subnets

[ytsarev]

Description of your changes

Assign service type labels to database subnets

will be used by configuration-azure-database for effective subnet selection

I have:

• Read and followed Upbound's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR, as appropriate.

How has this code been tested

up test run tests/*
  ✓   Parsing tests
  ✓   Checking dependencies
  ✓   Generating language schemas
  ✓   Building functions
  ✓   Checking dependencies
  ✓   Generating language schemas
  ✓   Building functions                                                                                                                   ✓   Checking dependencies                                                                                                                ✓   Generating language schemas
  ✓   Building functions
  ✓   Checking dependencies                                                                                                                ✓   Generating language schemas                                                                                                          ✓   Building functions
  ✓   Checking dependencies
  ✓   Generating language schemas                                                                                                          ✓   Building functions                                                                                                                   ✓   Building configuration package
  ✓   Pushing embedded functions to local daemon
  ✓   Assert test-xnetwork-with-postgresql-db                                                                                              ✓   Assert test-xnetwork-with-mysql-db                                                                                                   ✓   Assert test-xnetwork-without-db
  ✓   Assert test-xnetwork-with-multiple-dbs
 SUCCESS
 SUCCESS  Tests Summary:
 SUCCESS  ------------------
 SUCCESS  Total Tests Executed: 4
 SUCCESS  Passed tests:         4
 SUCCESS  Failed tests:         0