yaml: case-sensitivity of `name` field

## Bug Report

**Describe the bug**

Regression from 3.1 series, the `name` field of the plugin has to be lowercase whereas previously it could be any-case.

**To Reproduce**

```shell
$ cat fluent-bit.yaml
pipeline:
inputs:
- tag: dummy.4aaf0fd6-0f0c-47a3-92b1-7432382f5f3f
Name: dummy
rate: 1
dummy: '{"message":"dummy"}'
samples: 0
start_time_sec: -1
start_time_nsec: -1
outputs:
- name: stdout
Match_Regex: .{0,}

$ docker run --rm -it -v $PWD/fluent-bit.yaml:/fluent-bit.yaml:ro fluent/fluent-bit:3.1.7 -c /fluent-bit.yaml
Fluent Bit v3.1.7
* Copyright (C) 2015-2024 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io/

______ _ _ ______ _ _ _____ __
| ___| | | | | ___ (_) | |____ |/ |
| |_ | |_ _ ___ _ __ | |_ | |_/ /_| |_ __ __ / /`| |
| _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / / \ \ | |
| | | | |_| | __/ | | | |_ | |_/ / | |_ \ V /.___/ /_| |_
\_| |_|\__,_|\___|_| |_|\__| \____/|_|\__| \_/ \____(_)___/

[2024/12/17 17:18:58] [ info] [fluent bit] version=3.1.7, commit=c6e902a43a, pid=1
[2024/12/17 17:18:58] [ info] [storage] ver=1.5.2, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/12/17 17:18:58] [ info] [cmetrics] version=0.9.5
[2024/12/17 17:18:58] [ info] [ctraces ] version=0.5.5
[2024/12/17 17:18:58] [ info] [input:dummy:dummy.0] initializing
[2024/12/17 17:18:58] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2024/12/17 17:18:58] [ info] [sp] stream processor started
[2024/12/17 17:18:58] [ info] [output:stdout:stdout.0] worker #0 started
[0] dummy.4aaf0fd6-0f0c-47a3-92b1-7432382f5f3f: [[1734455938.961654839, {}], {"message"=>"dummy"}]
[0] dummy.4aaf0fd6-0f0c-47a3-92b1-7432382f5f3f: [[1734455939.963836757, {}], {"message"=>"dummy"}]
^C[2024/12/17 17:19:01] [engine] caught signal (SIGINT)
[2024/12/17 17:19:01] [ warn] [engine] service will shutdown in max 5 seconds
[0] dummy.4aaf0fd6-0f0c-47a3-92b1-7432382f5f3f: [[1734455940.963912840, {}], {"message"=>"dummy"}]
[2024/12/17 17:19:01] [ info] [input] pausing dummy.0
[2024/12/17 17:19:01] [ info] [engine] service has stopped (0 pending tasks)
[2024/12/17 17:19:01] [ info] [input] pausing dummy.0
[2024/12/17 17:19:01] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2024/12/17 17:19:01] [ info] [output:stdout:stdout.0] thread worker #0 stopped
$ docker run --rm -it -v $PWD/fluent-bit.yaml:/fluent-bit.yaml:ro fluent/fluent-bit:3.2.2 -c /fluent-bit.yaml
Fluent Bit v3.2.2
* Copyright (C) 2015-2024 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io/

______ _ _ ______ _ _ _____ _____
| ___| | | | | ___ (_) | |____ |/ __ \
| |_ | |_ _ ___ _ __ | |_ | |_/ /_| |_ __ __ / /`' / /'
| _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / / \ \ / /
| | | | |_| | __/ | | | |_ | |_/ / | |_ \ V /.___/ /./ /___
\_| |_|\__,_|\___|_| |_|\__| \____/|_|\__| \_/ \____(_)_____/

[2024/12/17 17:19:09] [error] [config] section 'input' is missing the 'name' property
[2024/12/17 17:19:09] [error] configuration file contains errors, aborting.
```