increase CAPMVM manager default resources

Nobody has claimed this yet.

**What happened:**
During the initial rollout of CAPMVM we noticed that the manager was crashlooping. We had only one resource to reconcile and no pre-existing clusters or any interfering objects configured in the same namespace. The logical choice was bumping the controller resources from cpu 100m /mem 30m until we felt like the controller was stable. once we reached 300m / 300m the controller began and continued without restart. We doubled every time so Im sure it can be tuned lower.

**What did you expect to happen:**
CAPMVM to stay up without issue

**How to reproduce it:**

provide a single resource after deploying on existing deployment resources.

**Anything else you would like to add:**
https://github.com/weaveworks-liquidmetal/cluster-api-provider-microvm/blob/64cb6accd075354a78ad31fee0129f56633dfc50/config/manager/manager.yaml#L39 but would like to performance

**Environment:**
6 node virtualised cluster. nodes are 4 core 16Gb RAM.

- capmvm version:
v0.8.0

- OS (e.g. from `/etc/os-release`):
Ubuntu 20.04

Start with config/manager/manager.yaml at the linked manager resource settings and inspect the defaults used for the CAPMVM controller. Reproduce deployment with one resource on the stated environment, then adjust and validate the CPU and memory settings until the manager stays running without crashlooping.

Written by the indexing model from the issue text.