out_azure_blob: add path templating support comparable to s3

[nberlee]

fixes #7515

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Enter [N/A] in the box, if an item is not applicable to your change.

Testing
Before we can approve your change; please submit the following in a comment:

• [ X] Example configuration file for the change

[SERVICE]
    flush     1
    log_level info

[INPUT]
    name      dummy
    dummy     {"name": "Fluent Bit", "year": 2020}
    samples   1
    tag       app.log


[OUTPUT]
    name                  azure_blob
    match                 *
    account_name          devstoreaccount1
    shared_key            Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==
    path                  logs/$TAG/%Y/%m/%d/$UUID
    container_name        devstoreaccount1
    auto_create_container on
    tls                   off
    emulator_mode         on
    endpoint              http://localhost:10000

• Debug log output from testing the change
  see valgrind log

• Attached Valgrind output that shows no leaks or memory corruption was found
  valgrind.log

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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