[docs][7.3] documentation backports

[bmorelli25]

• [docs] Update Logstash output documentation ([docs] Update Logstash output documentation #2691)
• [docs] APM Server install and run structure ([docs] APM Server install and run structure #2170)
• [docs] Update current branch for dotnet-branch ([docs] Update current branch for dotnet-branch #2701)
• [docs] Add and improve SSL/TLS documentation ([docs] Add and improve SSL/TLS documentation #2715)
• [docs] Update link for "ccr-overview-beats" anchor ([docs] Update link for "ccr-overview-beats" anchor #2589)

[bmorelli25]

This requires changes in the RUM repo:

07:04:53 INFO:build_docs:Bad cross-document links:
07:04:53 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/rum-js/2.x/sourcemap.html:
07:04:53 INFO:build_docs:   - en/apm/server/current/securing-apm-server.html#secret-token
07:04:53 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/rum-js/3.x/sourcemap.html:
07:04:53 INFO:build_docs:   - en/apm/server/current/securing-apm-server.html#secret-token
07:04:53 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/rum-js/4.x/sourcemap.html:
07:04:53 INFO:build_docs:   - en/apm/server/current/securing-apm-server.html#secret-token
07:04:53 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/rum-js/current/sourcemap.html:
07:04:53 INFO:build_docs:   - en/apm/server/current/securing-apm-server.html#secret-token
07:04:53 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/rum-js/master/sourcemap.html:
07:04:53 INFO:build_docs:   - en/apm/server/current/securing-apm-server.html#secret-token

The new/correct link is:

{apm-server-ref}/secure-communication-agents.html#secret-token[]

[bmorelli25]

Rum links fixed in:
elastic/apm-agent-rum-js#431
elastic/apm-agent-rum-js#428
elastic/apm-agent-rum-js#429
elastic/apm-agent-rum-js#430