Add --trim-blocks and --lstrip-blocks

[kenji-myk]

It's helpful if we can use trim_blocks and lstrip_blocks rendering options.

Explaining with a sample in https://ttl255.com/jinja2-tutorial-part-3-whitespace-control/.

sample.jinja2:

{% for iname, idata in interfaces.items() %}
interface {{ iname }}
 description {{ idata.description }}
  {% if idata.ipv4_address is defined %}
 ip address {{ idata.ipv4_address }}
  {% endif %}
{% endfor %}

input.yaml:

interfaces:
  Ethernet1:
    description: capture-port
  Ethernet2:
    description: leaf01-eth51
    ipv4_address: 10.50.0.0/31

• No option

$ jinja2 sample.jinja2 input.yaml

interface Ethernet1
 description capture-port


interface Ethernet2
 description leaf01-eth51

 ip address 10.50.0.0/31

• Only --trim-blocks

jinja2 sample.jinja2 input.yaml --trim-blocks
interface Ethernet1
 description capture-port
  interface Ethernet2
 description leaf01-eth51
   ip address 10.50.0.0/31
  ⏎

• Both --trim-blocks and --lstrip-blocks

$ jinja2 sample.jinja2 input.yaml --trim-blocks --lstrip-blocks
interface Ethernet1
 description capture-port
interface Ethernet2
 description leaf01-eth51
 ip address 10.50.0.0/31

[kenji-myk]

@mattrobenolt Could you also review this? 🙇