Add configurable LDAP timeout properties

[filip-daca]

This PR adds 2 new fields to configure LDAP timeouts. Without it, no timeout was used, which could lead to LDAP connectivity issues causing deadlocks while accessing synchronised user cache provided by Guava.

Verification

• new fields in UI:

• timeouts used visible in logs:

Sep 12, 2022 1:27:21 PM FINE org.acegisecurity.ldap.DefaultInitialDirContextFactory connect
Creating InitialDirContext with environment {java.naming.factory.initial=com.sun.jndi.ldap.LdapCtxFactory, java.naming.referral=follow, java.naming.security.principal=***, com.sun.jndi.ldap.connect.timeout=30000, com.sun.jndi.ldap.connect.pool=true, com.sun.jndi.ldap.read.timeout=60000, java.naming.provider.url=ldaps://****:636/dc=***, java.naming.security.authentication=simple, java.naming.security.credentials=******}

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[sboardwell]

Hi @filip-daca, thanks a lot for the PR. Instead of adding additional fields, do you think you could base your solution on environment variables as done in jenkinsci/ldap-plugin#102?

This would keep mean less maintenance and helps keep things aligned with the main ldap plugin.