add opentelemetry output

[evanzhang87]

use add_fields to build formatted fields, then send to OLPT server, just support log now

const (
    resourcePrefix       = "oltp_resource_"
    scopePrefix          = "oltp_scope_"
    scopeName            = "oltp_scope_name"
    scopeVersion         = "oltp_scope_version"
    scopeSchemaUrl       = "oltp_scope_schemaurl"
    recordPrefix         = "oltp_logrecords_"
    recordTime           = "oltp_logrecords_time"
    recordSeverity       = "oltp_logrecords_severity"
    recordSeverityNumber = "oltp_logrecords_severitynumber"
    recordFlags          = "oltp_logrecords_flags"
    recordTraceId        = "oltp_logrecords_traceid"
    recordSpanId         = "oltp_logrecords_spanid"
    recordBody           = "oltp_logrecords_body"
)

type OLTPOutputConfig struct {
    ServiceAddress string `json:"service_address"` // default localhost:4317
    ClientAuthConfig
    Timeout     int               `json:"timeout"` // default 5s
    Compression string            `json:"compression"` // default none
    Headers     map[string]string `json:"headers"` // grpc headers
}

type ClientAuthConfig struct {
    TLSCA               string `json:"tls_ca"`
    TLSCert             string `json:"tls_cert"`
    TLSKey              string `json:"tls_key"`
    TLSKeyPwd           string `json:"tls_key_pwd"`
    TLSMinVersion       string `json:"tls_min_version"`
    InsecureSkipVerify  bool   `json:"insecure_skip_verify"`
    ServerName          string `json:"tls_server_name"`
    RenegotiationMethod string `json:"tls_renegotiation_method"`
    Enable              *bool  `json:"tls_enable"`
}

update GoVersion to 1.19, it's needed by opentelemetry, and 1.13 was too old, it's time to try new GO!

[childe]

Thanks very much for your PR, but according to my current plan, I'm not intending to add any more OUTPUTs. If you could provide a plugin-style codec & output, I'm pleased to add its link to Readme.

PS: refer to https://go.dev/ref/mod#go-mod-file-go:

The go directive sets the minimum version of Go required to use this module.

[codecov-commenter]

Codecov Report

Attention: 188 lines in your changes are missing coverage. Please review.

Comparison is base (5c04854) 32.62% compared to head (566c3ba) 31.96%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #234 +/- ## ========================================== - Coverage 32.62% 31.96% -0.66% ========================================== Files 53 55 +2 Lines 4377 4611 +234 ========================================== + Hits 1428 1474 +46 - Misses 2794 2973 +179 - Partials 155 164 +9 ``` | [Flag](https://app.codecov.io/gh/childe/gohangout/pull/234/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/childe/gohangout/pull/234/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `31.96% <19.65%> (-0.66%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/childe/gohangout/pull/234?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [codec/oltp\_encoder.go](https://app.codecov.io/gh/childe/gohangout/pull/234?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29kZWMvb2x0cF9lbmNvZGVyLmdv) | `0.00% <0.00%> (ø)` | | | [output/oltp\_output.go](https://app.codecov.io/gh/childe/gohangout/pull/234?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-b3V0cHV0L29sdHBfb3V0cHV0Lmdv) | `29.11% <29.11%> (ø)` | |

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[evanzhang87]

That's ok, learn from you!