Fix: Inserting VP into txtFields in Advertiser_ImplMinimalMdns

[sharadb-amazon]

Problem

• VP was not being inserted into the array of txtFields in the mDNS Advertiser
• VendorId's presence was not being checked before setting the value of VP

Change overview

Inserted VP's value into txtFields and checked vendorId's presence

Testing

• Tested by running chip-lighting-app for linux and querying using avahi-browse -ar to see that VP field is advertised now.

[github-actions]

Size increase report for "esp32-example-build" from e250a8c

File	Section	File	VM
chip-all-clusters-app.elf	.flash.text	28	28

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_line,0,114
.debug_loc,0,86
.flash.text,28,28
.debug_ranges,0,8
.debug_info,0,-2
.debug_str,0,-2